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United States Patent 7,649,046 Pham , et al.January 19, 2010
Modified polypropylene composition
Abstract
The invention relates to a polypropylene composition a heterophasic propylene copolymer, an elastomeric copolymer and inorganic filler and to a method for producing the propylene composition using peroxides. The composition is characterised by a combination of excellent impact strength, stiffness, elasticity and surface stability.
Inventors: Pham; Tung (Linz, AT), Reichelt; Norbert
(Neuhofen/Krems, AT), Stadlbauer; Manfred (Linz,
AT)
Assignee: Borealis Technology Oy (Porvoo, FI)
Appl. No.: 11/629,945
Filed: June 17, 2005
PCT Filed: June 17, 2005
PCT No.: PCT/EP2005/006535
371(c)(1),(2),(4)
Date:
January 29, 2007
PCT Pub. No.: WO2005/123827
PCT Pub. Date: December 29, 2005
Foreign Application Priority Data
Jun 18, 2004 [EP] 04102801
Current U.S. Class:524/515 ; 524/525; 524/528
Current International Class: C08K 5/00 (20060101); B01F 17/00 (20060101); C08J 3/22 (20060101)
Field of Search: 524/515,525,528
References Cited [Referenced By]
U.S. Patent Documents
6077907June 2000 Raetzsch et al.
2002/0082328June 2002 Yu et al.
2004/0116607June 2004 Malm et al.
Foreign Patent Documents
1 236 769 Sep., 200
2 EP 1236769 Sep., 2002 EP
1 354 901 Oct., 2003 EP
1 391 428 Feb., 2004 EP Primary Examiner: Choi; Ling-Siu
Assistant Examiner: Chin; Hui
Attorney, Agent or Firm: Jordan and Hamburg LLP
Claims
The invention claimed is:
1. Polypropylene composition comprising A) 70-99 parts by weight of a heterophasic propylene copolymer comprising 60-90 wt % of a matrix phase comprising a propylene homopolymer having an isotacticity
IR.tau..gtoreq.0.970, and 10-40 wt % of an elastomeric copolymer comprising 20-55 wt % of ethylene and 80-45 wt % of one or more
C.sub.3-C.sub.8 .alpha.-olefins, B) 1-30 parts by weight of a further elastomeric copolymer comprising an ethylene-.alpha.-olefin elastomer, with more than 65 wt % of ethylene and up to 35 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins, where a disperse phase is comprised
of the elastomeric copolymers, and C) 3-25 parts by weight of an inorganic filler, the polypropylene composition having a Charpy notched impact strength according to ISO 179/1eA at +23.degree. C.
of .gtoreq.55.0 kJ/m.sup.2, a Charpy notched impact strength
according to ISO 179/1eA at -20.degree. C. of .gtoreq.7.0 kJ/m.sup.2, a tensile modulus according to ISO 527-3 of .gtoreq.1200 Mpa
elasticity (elongation at break) according to ISO 527-3 of .gtoreq.80%
and an average failure length (AFL), which is determined by injection moulding the composition into a test specimen having the dimensions
of 150.times.80.times.2 mm, creating surface defects by directing a water jet (76 bar; 60.degree. C., flat spray nozzle 1/4 PMEG 2506) from a distance of 8 cm (from nozzle to specimen surface) at the specimen surface at three different locations at a distance of 6 cm from each location and for 60 sec each, measuring the length of each surface defect and calculating the average value of the three locations, of .ltoreq.10 mm.
2. Polypropylene composition according to claim 1, further comprising 5-20 parts by weight of inorganic filler.
3. Polypropylene composition according to claim 2, wherein the polypropylene composition comprises A) 75-85 parts per weight of the heterophasic propylene copolymer, B) 5-15 parts by weight of the further elastomeric copolymer and C) 5-15 parts per weight of the inorganic filler.
4. Polypropylene composition according to one of claims 1 to 3, wherein the polypropylene composition further comprises from 0.01 to 10 parts by weight, based on total weight of the composition, of at least one chemically bound, bifunctionally unsaturated monomer and/or multifunctionally unsaturated low molecular weight polymer having a molecular weight M.sub.n.ltoreq.10000 g/mol.
5. Polypropylene composition according to claim 4, wherein the polypropylene composition comprises one or more of chemically bound butadiene, isoprene, dimethylbutadiene, divinylbenzene and polybutadiene.
6. Method for producing a polypropylene composition according to
claim 1 comprising homogenising an educt mixture comprising A) 70-99 parts by weight of a heterophasic propylene copolymer comprising 60-
90 wt % of a matrix phase comprising a propylene homopolymer having
an isotacticity IR.tau..gtoreq.0.970, and 10-40 wt % of an
elastomeric copolymer comprising 20-55 wt % of ethylene and 80-45 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins, B) 1-30 parts by
weight of a further elastomeric copolymer comprising an ethylene-
.alpha.-olefin elastomer, with more than 65 wt % of ethylene and up to 35 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins, C) 3-25 parts by weight of an inorganic filler, and D) 0.05-3 parts by weight of an organic peroxide having a half life time t(1/2) at 110.degree.
C. of >6 min and a half life time t(1/2) at 150.degree. C. of <6 min the mixture being in a molten state, heating the melt to 220-
250.degree. C. to remove unreacted compounds and decomposition products, cooling and pelletising.
7. Method according to claim 6, wherein the educt mixture further comprises 0.01-10 parts by weight of at least one bifunctionally unsaturated monomer and/or multifunctionally unsaturated low molecular weight polymer having a molecular weight
M.sub.n.ltoreq.10000 g/mol.
8. Method according to claim 6, comprising mixing A) 70-99 parts by weight of a heterophasic propylene copolymer comprising 60-90 wt % of a matrix phase comprising a propylene homopolymer having an isotacticity IR.tau..gtoreq.0.970, and 10-40 wt % of an elastomeric copolymer comprising 20-55 wt % of ethylene and 80-45 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins, with B) 1-30 parts by weight of a further elastomeric copolymer comprising an ethylene-.alpha.-olefin elastomer, with more than 65 wt % of ethylene and up to 35 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins, and C) 3-25 parts by weight of an inorganic filler, and heating and melting the mixture, adding from 0.05 to 3 parts by weight of the organic peroxide
directly into the polymer melt, homogenising and heating the melt to 220-250.degree. C. to remove unreacted compounds and decomposition products, cooling and pelletising.
9. Method according to claim 6, comprising dosing the polymer components A) 70-99 parts by weight of a heterophasic propylene copolymer comprising 60-90 wt % of a matrix phase comprising a propylene homopolymer having an isotacticity IR.tau..gtoreq.0.0970, and 10-40 wt % of an elastomeric copolymer comprising 20-55 wt % of ethylene and 80-45 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins, B) 1-30 parts by weight of a further elastomeric copolymer
comprising an ethylene-.alpha.-olefin elastomer, with more than 65
wt % of ethylene and up to 35 wt % of one or more C.sub.3-
C.sub.8 .alpha.-olefins, into a melting mixing device, heating and melting the mixture, adding C) 3-25 parts by weight of an inorganic filler into the melt, adding from 0.05 to 3 parts per weight of the organic peroxide directly into the polymer melt, homogenising and heating the melt to 220-250.degree. C. to remove unreacted compounds and decomposition products, cooling and pelletising.
10. Method according to claim 8 or 9, further comprising adding 0.01-10 parts by weight of at least one bifunctionally unsaturated monomer and/or multifunctionally unsaturated low molecular weight polymer having a molecular weight M.sub.n.ltoreq.10000 g/mol into the polymer melt together with the addition of the peroxide and/or during the homogenising step.
11. Method according to claim 6, comprising dosing the polymer components A) 70-99 parts by weight of a heterophasic propylene copolymer comprising 60-90 wt % of a matrix phase comprising a propylene homopolymer having an isotacticity IR.tau..gtoreq.0.970, and 10-40 wt % of an elastomeric copolymer comprising 20-55 wt % of ethylene and 80-45 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins, B) 1-30 parts by weight of a further elastomeric copolymer comprising an ethylene-.alpha.-olefin elastomer, with more than 65
wt % of ethylene and up to 35 wt % of one or more C.sub.3-
C.sub.8 .alpha.-olefins, and 0.05 to 3 parts by weight of the organic peroxide into a melt mixing device, heating and melting the mixture, adding C) 3-25 parts by weight of an inorganic filler into the melt, homogenising and heating the melt to 220-250.degree. C. to remove unreacted compound and decomposition products, cooling and pelletising.
12. Method according to claim 11, further comprising adding 0.01-10 parts by weight of at least one bifunctionally unsaturated monomer and/or multifunctionally unsaturated low molecular weight polymer having a molecular weight M.sub.n.ltoreq.10000 g/mol into the melt mixing device together with the polymer components A and B.
13. Method according to claim 8, 9 or 11, wherein the melt mixing device is an extruder.
Description
BACKGROUND OF THE INVENTION
The invention relates to novel modified polypropylene compositions, especially for automobile exterior applications. More particularly, the invention relates to modified polypropylene compositions comprising a heterophasic propylene copolymer, a further elastomeric copolymer and an inorganic filler. The modified composition has excellent properties, especially impact strength, stiffness,
elasticity and surface stability.
The automotive market increasingly requires polypropylene compounds for car exterior applications having a performance which is not achievable with conventional compounding. One of the critical requirements for exterior applications in many cases is the high surface stability of the moulded parts which are painted such as bumper, body panels etc.
It is well known that the mechanical performance of
polypropylene/rubber compounds is determined by the phase structure and thus composition morphology. With low molecular weight rubbers (reactor made and externally), the tensile elongation of the final filler compounds for typical exterior applications is improved. However, the low molecular weight rubber fraction causes unsatisfactory surface stability, which results in unsatisfactory paint adhesion.
The main reason for the low surface stability was identified to be in the surface structure of the moulded part. Studies (Moffitt et al; J. Pol. Sci. 40 (2002), 2842; Ryntz; Proc. Org. Coat. 27 (1996), 241)) have shown that when a polypropylene/rubber system is injection moulded, the surface morphology of formed parts, due to the shear
induced crystallisation, could be described as a surface layer of a polypropylene rich region, beneath which a rubber (particles) rich layer lies.
Surface stability of such multiphase polymer systems
(polypropylene/rubber) depends very strongly on the phase separation behaviour in the surface region. The role of interface management between polypropylene and rubber phases in this region e.g. control
of miscibility between the components is a major factor affecting the ability of the moulded part to resist surface damage caused by
external forces. Stresses applied to the polypropylene/rubber part in form of compressive shearing events, e.g. scratches, gouges etc.
often result in cohesive debondment due to the week phase adhesion of the systems appearing in form of "ripping" of the surface region (10-100 .mu.m). The cohesive failure is a result of improperly controlled phase bounding arising by incompatibility between two polymers (Ryntz, ACS Symp. Ser. 805 (2002), 266).
There exists a continuing need for new polypropylene compositions for injection moulding of automobile exterior parts, where the compositions or the injection moulded parts produced therefrom have
to fulfill the following requirements simultaneously: High impact strength, high stiffness, high elasticity, high surface stability.
SUMMARY OF THE INVENTION
The above object has been achieved by a polypropylene composition comprising
A) 70-99 parts per weight of a heterophasic propylene copolymer comprising 60-90 wt % of a matrix phase comprising a propylene homopolymer having an isotacticity IR.tau..gtoreq.0.970, and 10-40
wt % of an elastomeric copolymer comprising 20-55 wt % of ethylene
and 80-45 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins,
B) 1-30 parts per weight of a further elastomeric copolymer
comprising an ethylene-.alpha.-olefin elastomer, with more than 65
wt % of ethylene and up to 35 wt % of one or more C.sub.3-
C.sub.8 .alpha.-olefins, where a disperse phase is comprised of the elastomeric copolymers, and
C) 3-25 parts per weight of an inorganic filler,
the polypropylene composition having
a Charpy notched impact strength according to ISO 179/1 eA at
+23.degree. C. of .gtoreq.55.0 kJ/m.sup.2, a Charpy notched impact strength according to ISO 179/1 eA at -20.degree. C. of .gtoreq.7.0 kJ/m.sup.2, a tensile modulus according to ISO 527-3 of .gtoreq.1200 MPa elasticity (elongation at break) according to ISO 527-3
of .gtoreq.80% and an average failure length (AFL), which is determined by injection moulding the composition into a test specimen having the dimensions of 150.times.80.times.2 mm, creating surface defects by directing a water jet (76 bar; 60.degree. C., flat spray nozzle 1/4 PMEG 2506) from a distance of 8 cm (from nozzle to specimen surface) at the specimen surface at three different
locations at a distance of 6 cm from each location and for 60 sec each, measuring the length of each surface defect and calculating the average value of the three locations, of .ltoreq.10 mm.
The new compositions shall be used for injection moulding. The MFR of the compositions shall not exceed 15 g/10 min, preferred are MFR-values of s 8 g/10 min. A Charpy notched impact strength according to ISO 179/1 eA at +23.degree. C. of .gtoreq.55.0 kJ/m.sup.2, better
of .gtoreq.60 kJ/m.sup.2 and, still better, of .gtoreq.65.0
kJ/m.sup.2 is considered as "high impact strength". Minimum values
for the Charpy notched impact strength according to ISO 179/1eA at -20.degree. C. are .gtoreq.7.0 kJ/m.sup.2, better >8.0 kJ/m.sup.2 and still better, >8.5 kJ/m.sup.2. Stiffness is considered to be high with tensile moduli according to ISO 527-3 of .gtoreq.1200 MPa. Still higher values are of course more preferable. Elasticity is considered to be high when elongation at break according to ISO 527-3
is .gtoreq.80%, preferably .gtoreq.100%. The surface stability of injection moulded parts is considered to be high, when the average failure length (AFL), determined according to the procedure described in the experimental section, is .ltoreq.10 mm, preferably .ltoreq.8
mm. Still more preferred are AFL values .ltoreq.5 mm.
It has surprisingly been found, that polypropylene compositions containing the components A, B and C which are then modified using specific organic peroxides will result in new polypropylene compositions where the previous property profile regarding impact strength, stiffness and elasticity is largely retained, but where also a sudden increase in surface stability is observed.
The new polypropylene compositions are characterised by simultaneous high levels of impact strength, stiffness, elasticity and surface stability. The high surface stability is believed to be due to an improved adhesion between matrix phase and disperse phase.
The new polypropylene compositions are obtained by treating compositions containing the components A, B and C with specific organic peroxides.
The matrix phase of the heterophasic propylene copolymer comprises a propylene homopolymer. The matrix phase is present in an amount of
60-90 wt %, preferably 70-20 wt %, based on the total amount of heterophasic propylene copolymer.
The homopolymer part of the heterophasic propylene copolymer preferably has an isotacticity IR.tau. of .gtoreq.0.970, preferably 0.970-0.995.
The IR.tau. of a propylene polymer is determined by Infrared spectroscopy and calculated as described in EP 0 277 514 A2 on page 3 (especially column 3, line 37 to column 4, line 30) and page 5 (column 7, line 53 to column 8, line 11).
The elastomeric copolymer which comprises the disperse phase of the heterophasic copolymer and which also comprises--together with the further elastomeric copolymer--a disperse phase of the entire composition, is present in an amount of from 10-40 wt %, preferably 20-30 wt %, based on the total amount of heterophasic propylene copolymer.
The elastomeric copolymer is comprised of from 20-55 wt % preferably 30-50 wt % of ethylene and 80-45 wt % preferably 70-50 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins. The .alpha.-olefin is
preferably selected from the list of propylene, 1-butene, 1-pentene,
4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene, where propylene, 1-butene and 1-octene are particularly preferred.
A further elastomeric copolymer is present in an amount of from 1-30 parts per weight. The further elastomeric copolymer comprises an ethylene-.alpha.-olefin elastomer, which comprises more than 65 wt %
of ethylene and up to 35 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins. As with the first elastomeric copolymer, the .alpha.-olefin
is preferably selected from the list of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene, where propylene, 1-butene and 1-octene are particularly preferred.
The polypropylene composition comprises 3-25 parts per weight of an inorganic filler. Preferred as inorganic filler are talc, mica, wollastonite and chalk.
According to a preferred embodiment, the polypropylene composition comprises 5-20 parts per weight of inorganic filler.
Inorganic filler can be added to the composition before and/or during the modification with the organic peroxides. It is preferred to add
at least a substantial amount, e.g. at least about 50%, of the inorganic filler before and/or during the modification treatment. It
is particularly preferred to add the entire amount of inorganic
filler before and/or during the modification treatment.
DETAILED DESCRIPTION OF THE INVENTION
According to a preferred embodiment of the present invention, the polypropylene composition comprises A) 75-85 parts per weight of the heterophasic propylene copolymer, B) 5-15 parts per weight of the further elastomeric copolymer and C) 5-20 parts per weight of the inorganic filler.
A particularly advantageous property profile is achievable with the above composition, i.e. with the above concentrations of heterophasic and further elastomeric copolymer and when
the entire amount of filler is added to the composition before/during the modification treatment.
According to a further advantageous embodiment the polypropylene composition comprises from 0.01 to 10 parts per weight based on the weight of the polypropylene composition of a chemically bound bifunctionally unsaturated monomer and/or multifunctionally unsaturated low molecular weight polymer having a molecular weight M.sub.n.ltoreq.10000 g/mol. synthesised from one and/or more unsaturated monomers.
"Bifunctionally or multifunctionally unsaturated" as used above means the presence of two or more non-aromatic double bonds, as in e.g. divinylbenzene or cyclopentadiene or polybutadiene. Only such bi- or multifunctionally unsaturated compounds are used which can be polymerised with the aid of free radicals. The unsaturated sites in the bi- or multifunctionally unsaturated compounds are in their chemically bound state not actually "unsaturated", because the double bonds are each used for a covalent bond to the polymer chains of the matrix polymer and/or the elastomeric copolymer.
Reaction of the bifunctionally unsaturated monomer and/or multifunctionally unsaturated low molecular weight polymer having a molecular weight M.sub.n.ltoreq.10000 g/mol, synthesised from one
and/or more unsaturated monomers with the heterophasic polymer may be performed in the presence of a free radical forming agent, e.g. a thermally decomposable peroxide, ionising radiation or microwave radiation.
The bifunctionally unsaturated monomers may be divinyl compounds, such as divinylaniline, m-divinylbenzene, p-divinylbenzene, divinylpentane and divinylpropane; allyl compounds, such as allyl acrylate, allyl methacrylate, allyl methyl maleate and allyl vinyl
ether; dienes, such as 1,3-butadiene, chloroprene, cyclohexadiene, cyclopentadiene, 2,3-dimethylbutadiene, heptadiene, hexadiene, isoprene and 1,4-pentadiene; aromatic and/or aliphatic bis(maleimide) and bis(citraconimide) compounds and mixtures of these unsaturated monomers.
The multifunctionally unsaturated low molecular weight polymer having a molecular weight M.sub.n.ltoreq.10000 g/mol may be synthesised from one or more unsaturated monomers. Examples of such low molecular weight polymers are polybutadienes, especially where the different microstructures in the polymer chain, i.e. 1,4-cis, 1,4-trans and
1,2-(vinyl) configuration are predominantly in the 1,2-(vinyl) configuration copolymers of butadiene and styrene having 1,2-(vinyl) configuration in the polymer chain.
In the polypropylene composition of the invention the chemically bound bifunctionally unsaturated monomer and/or multifunctionally unsaturated low molecular weight polymer act as coupling agent between the matrix polymer and the elastomeric copolymers of the disperse phase. It is believed that those molecules, which--with one of their functionalities--are bound to a polymer molecule of the matrix polymer and--with their second or one of their further functionalities--are bound to a polymer molecule belonging to the disperse phase, effect the coupling action and thus promote dispersion of the elastomeric copolymers within the matrix phase.
Preferred bifunctionally unsaturated monomers are 1,3-butadiene, isoprene, dimethyl butadiene and divinylbenzene.
Preferred low molecular weight polymer is polybutadiene, in
particular a polybutadiene having more than 50 wt % of the butadiene in the 1,2-(vinyl) configuration.
The polypropylene composition may contain more than one
bifunctionally unsaturated monomer and/or low molecular weight polymer.
In connection with the above it is particularly preferred that the
modified polypropylene composition of the invention contains from 0.1 to 3 wt % based on the weight of the composition of a chemically bound bifunctionally unsaturated monomer and/or multifunctionally unsaturated low molecular weight polymer having a molecular weight
M.sub.n.ltoreq.10000 g/mol.
While measurable effects are already observed with small concentrations of bifunctionally unsaturated monomer and/or multifunctionally unsaturated low molecular weight polymer (depending also on the nature of the monomer and/or polymers) it is preferred
that the polypropylene composition contains at least 0.1 wt % of the bifunctionally unsaturated monomer and/or multifunctionally unsaturated polymer.
With increasing amounts of bifunctionally unsaturated monomer and/or multifunctionally unsaturated polymer, an influence on the mechanical parameters of the polypropylene composition makes itself noticeable, which is not related to the coupling effect. It is therefore
preferred that the modified polypropylene composition contains not more than 3 parts per weight of the bifunctionally unsaturated monomer and/or multifunctionally unsaturated polymer.
A further object is a method for producing the polypropylene compositions of the invention.
According to a basic embodiment, the polypropylene compositions are prepared by homogenising an educt mixture comprising A) 70-99 parts per weight of a heterophasic propylene copolymer comprising 60-90 wt % of a matrix phase comprising a propylene homopolymer having an isotacticity IR.tau..gtoreq.0.970, and 10-40 wt % of an elastomeric copolymer comprising 20-55 wt % of ethylene and 80-45 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins, B) 1-30 parts per weight of a further elastomeric copolymer comprising an ethylene-.alpha.-olefin elastomer, with more than 65 wt % of ethylene and up to 35 wt % of
one or more C.sub.3-C.sub.8 .alpha.-olefins, C) 3-25 parts per weight of an inorganic filler, and D) 0.05-3 parts per weight of an organic peroxide having a half life time t(1/2) at 110.degree. C. of >6 min and a half life time t(1/2) at 150.degree. C. of <6 min the mixture
being in a molten state, heating the melt to 220-250.degree. C. to remove unreacted compounds and decomposition products, cooling and pelletising.
Peroxides which are thermally decomposable upon the conditions of heating and melting the polymer/peroxide mixture and which meet the requirement of having a half life time t(1/2) at 110.degree. C. of >6 min and a half life time t(1/2) at 150.degree. C. of <6 min are suitable. The following organic peroxides are suitable for the above process:
Dibenzoyl peroxide, tert-Butyl peroxy-2-ethylhexanoate, tert-Amyl peroxy-2-ethylhexanoate, tert-Butyl peroxydiethylacetate, 1,4-
Di(tert-butylperoxycarbo)cyclohexane, tert-Butyl peroxyisobutyrate, 1,1-Di(tert-butylperoxy)-3,3,5-trimethyl-cyclohexane, Methyl isobutyl ketone peroxide, 2,2-Di(4,4-di(tert-butylperoxy)cyclohexyl)propane, 1,1-Di(tert-butylperoxy)cyclohexane, tert-Butyl peroxy-3,5,5-trimethylhexanoate, tert-Amylperoxy 2-ethylhexyl carbonate, 2,2-
Di(tert-butylperoxy)butane, tert-butylperoxy isopropyl carbonate,
tert-Butylperoxy 2-ethylhexyl carbonate, tert-Butyl peroxyacetate, tert-butyl peroxybenzoate, Di-tert-amyl peroxide and mixtures of these organic peroxides.
It has been observed, that peroxides used in conventional degradation processes exert different modes of action. One effect is, that the peroxides effect a breakage of the longest chains of the polymer molecules and, consequently, a corresponding decrease in viscosity of the polymer. A second effect is, that peroxide-induced radicals are recombining. Both effects are to a certain extent always present in peroxide induced degradation processes. The actual extent of each effect is influenced by the nature of the peroxide.
For the present invention it is preferred to use peroxides where the second mode of action is increased compared to "pure" degradation peroxides, and preferably where the second mode of action is predominant.
According to a preferred embodiment the employed peroxides are of the
above mentioned type and are selected from tert-butylperoxy isopropyl carbonate and tert-butyl peroxybenzoate.
During the homogenisation step the main part of the above described reaction(s) take place. Homogenisation usually takes from 5 to 60 seconds.
After homogenisation the melt is heated to 220-250.degree. C., in order to completely deactivate any remaining peroxide, to remove and deactivate any still unreacted compounds, e.g. radicals, and to remove decomposition products.
It is preferred, that the educt mixture further comprises 0.01-10
parts per weight of bifunctionally unsaturated monomers and/or multifunctionally unsaturated low molecular weight polymer having a molecular weight M.sub.n.ltoreq.10000 g/mol.
According to a more specific embodiment of the general procedure, the polypropylene composition is prepared by
mixing
A) 70-99 parts per weight of a heterophasic propylene copolymer comprising 60-90 wt % of a matrix phase comprising a propylene homopolymer having an isotacticity IR.tau..gtoreq.0.970, and 10-40
wt % of an elastomeric copolymer comprising 20-55 wt % of ethylene
and 80-45 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins, with B) 1-30 parts per weight of a further elastomeric copolymer comprising
an ethylene-.alpha.-olefin elastomer, with more than 65 wt % of ethylene and up to 35 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins, and C) 3-25 parts per weight of an inorganic filler, and heating and melting the mixture, preferably in an extruder, adding from 0.05 to 3 parts per weight of the organic peroxide directly into the polymer melt, homogenising and heating the melt to 220-250.degree.
C. to remove unreacted compounds and decomposition products, cooling and pelletising.
The polymers A and B and the filler C may be premixed before they are
dosed into the extruder. Alternatively, they may be dosed separately into the extruder.
Alternatively to the procedure above, the polypropylene compositions can also be prepared by dosing the polymer components
A) 70-99 parts per weight of a heterophasic propylene copolymer comprising 60-90 wt % of a matrix phase comprising a propylene homopolymer having an isotacticity IR.tau..gtoreq..about.0.970, and
10-40 wt % of an elastomeric copolymer comprising 20-55 wt % of ethylene and 80-45 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins,
B) 1-30 parts per weight of a further elastomeric copolymer
comprising an ethylene-.alpha.-olefin elastomer, with more than 65
wt % of ethylene and up to 35 wt % of one or more C.sub.3-
C.sub.8 .alpha.-olefins,
into a melt mixing device, preferably an extruder, heating and
melting the mixture,
adding C) 3-25 parts per weight of an inorganic filler into the melt,
adding from 0.05 to 3 parts per weight of the organic peroxide
directly into the polymer melt,
homogenising and heating the melt to 220-250.degree. C. to remove unreacted compounds and decomposition products,
cooling and pelletising.
This particular embodiment has the advantage, that the filler can be better dispersed in the polymer, because it is added into the melt. This requires less energy for homogeneously distributing the filler.
If unsaturated monomers and/or polymers are used in one of the latter two procedures, it is preferred to add 0.01-10 parts per weight of bifunctionally unsaturated monomers and/or multifunctionally
unsaturated low molecular weight polymer having a molecular weight M.sub.n.ltoreq.10000 g/mol into the polymer melt together with the addition of the peroxide and/or during the homogenising step.
It is preferred, that any unsaturated compounds are added before the homogenisation step is completed and before the melt is heated to
220-250.degree. C. for removing unreacted compounds and decomposition products.
According to a still further alternative of the basic embodiment, the polypropylene compositions are produced by dosing the polymer components
A) 70-99 parts per weight of a heterophasic propylene copolymer comprising 60-90 wt % of a matrix phase comprising a propylene homopolymer having an isotacticity IR.tau..gtoreq.0.970, and 10-40
wt % of an elastomeric copolymer comprising 20-55 wt % of ethylene
and 80-45 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins,
B) 1-30 parts per weight of a further elastomeric copolymer
comprising an ethylene-1-olefin elastomer, with more than 65 wt % of ethylene and up to 35 wt % of one or more C.sub.3-C.sub.8 .alpha.-olefins,
and 0.05 to 3 parts per weight of the organic peroxide
into a melt mixing device, preferably an extruder,
heating and melting the mixture,
adding C) 3-25 parts per weight of an inorganic filler into the melt,
homogenising and heating the melt to 220-250.degree. C. to remove unreacted compounds and decomposition products,
cooling and pelletising.
In this specific embodiment, it is preferred to add the 0.01-10 parts
per weight of bifunctionally unsaturated monomers and/or multifunctionally unsaturated low molecular weight polymer having a molecular weight M.sub.n.ltoreq.10000 g/mol into the melt mixing device together with the polymer components A and B.
If the unsaturated monomer and/or polymer is added into the polymer melt, it is preferably solvatised in an organic solvent, e.g. acetone, and the solution is injected into the polymermelt, e.g. into the extruder.
Alternatively, the unsaturated monomer and/or polymer, if for example in a liquid state, are absorbed in a polymer powder and are then added into the polymer melt in form of solid pellets.
Alternatively, the bifunctionally unsaturated monomer, if for example in a gaseous state, can be directly injected into the polymer melt without the aid of a solvent. Optionally, the bifunctionally unsaturated monomer can be applied as mixture with inert gases, e.g. nitrogen.
The educt heterophasic copolymer may be produced by multistage
process polymerisation of propylene and ethylene and/or an .alpha.-olefin such as bulk polymerisation, gas phase polymerisation, slurry polymerisation, solution polymerisation or combinations thereof using conventional catalysts. Those processes are well known to one skilled in the art.
A preferred process is a combination of a bulk slurry loop reactor(s) and gas phase reactor(s). The matrix polymer can be made either in loop reactors or in a combination of loop and gas phase reactor.
The polymer produced in this way is transferred into another reactor and the disperse phase, an ethylene/.alpha.-olefin rubber, is polymerised. Preferably this polymerisation step is done in a gas phase polymerisation.
A suitable catalyst for the polymerisation of the educt heterophasic propylene copolymer is any stereospecific catalyst for propylene
polymerisation which is capable of polymerising and copolymerising propylene and comonomers at a temperature of 40 to 110.degree. C. and at a pressure form 10 to 100 bar. Ziegler Natta catalysts as well as metallocene catalysts are suitable catalysts.
One skilled in the art is aware of the various possibilities to produce such heterophasic systems and will simply find out a suitable procedure to produce suitable educt heterophasic polyolefin compositions which are used in the present invention.
The educt heterophasic polyolefin composition may also be produced by mixing and melt blending a propylene homopolymer with an ethylene rubber copolymer.
An ethylene .alpha.-olefin elastomeric copolymer may be produced by known polymerisation processes such as solution, suspension and gas-phase polymerisation using conventional catalysts. Ziegler Natta catalysts as well as metallocene catalysts are suitable catalysts.
A widely used process is the solution polymerisation.
Ethylene, .alpha.-olefin and catalyst systems are polymerised in an excess of hydrocarbon solvent. Stabilisers and oils, if used, are added directly after polymerisation. The solvent and unreacted monomers are then flashed off with hot water or steam, or with mechanical devolatilisation. The polymer, which is in crumb form, is dried with dewatering in screens, mechanical presses or drying ovens. The crumb is formed into wrapped bales or extruded into pellets.
The suspension polymerisation process is a modification of bulk polymerisation. The monomers and catalyst system are injected into the reactor filled with .alpha.-olefin. The polymerisation takes place immediately, forming crumbs of polymer that are not soluble in the .alpha.-olefin. Flashing off the .alpha.-olefin and comonomer completes the polymerisation process.
The gas-phase polymerisation technology consists of one or more vertical fluidised beds. Monomers and nitrogen in gas form along with catalyst are fed to the reactor and solid product is removed
periodically. Heat of reaction is removed through the use of the circulating gas that also serves to fluidise the polymer bed. Solvents are not used, thereby eliminating the need for solvent stripping, washing and drying.
Measurement Methods
MFR
The melt flow rates were measured with a load of 2.16 kg at
230.degree. C. The melt flow rate is that quantity of polymer in grams which the test apparatus standardized to ISO 1133 extrudes within 10 minutes at a temperature of 230.degree. C. under a load of 2.16 kg.
Comonomer contents were measured with Fourier transform infrared spectroscopy (FTIR) calibrated with .sup.13C-NMR.
Tensile Test
Tensile test was performed according to ISO 527-3 using injection moulded specimens as described in EN ISO 1873-2 (dog bone shape, 3 mm thickness).
Charpy Notched Impact Strength
The Charpy notched impact strength was determined according to ISO 179/1 eA at 23.degree. C. and at -20.degree. C. by using injection moulded test specimens as described in EN ISO 1873-2
(80.times.10.times.4 mm).
Average Failure Length (AFL)
AFL was determined by injection moulding the composition into a test specimen having the dimensions of 150.times.80.times.2 mm, creating surface defects by directing a water jet (76 bar; 60.degree. C., flat spray nozzle 1/4 PMEG 2506, opening angle 25.degree.) using the high pressure cleaner system Limex Ehrle HDE600-24 kW with nozzle 1/4 PMEG
小学生作文批改方法及 步骤 公司内部档案编码：[OPPTR-OPPT28-OPPTL98-OPPNN08]
小学生作文批改方法及步骤第一步：学生自改作文 学生在练习本上写完自己的作文后，自己阅读、修改自己的作文。但是，学生个人修改，往往“只缘身在此山中”，而且限于水平，文章中的毛病，作者常常自己看不出来。 首先要求学生对自己的作文进行复看审核，查找出标点、错别字以及不通顺的句子，并进行改正。 接着从题意、中心、内容、感情、结构、语言等方面来一个“回头望”，多问几个“是什么”或“怎么样”，对自己的作文进行从点到面，实事求是的评价。 最后，对文章再次阅读，寻找出自己本次作文的最大亮点，或指出今后作文中应该改进的地方，在这样的自我修改，自我反思的过程中，学生的写作能力也在不断提高着。 第二步：小组内互改作文 组内成员都完成作文后，在组长的带领下，针对每一个组员的作文进行一一共同阅读，共同修改。 修改时要注意： 1格式是否正确。 2找出错别字。将错字在原文处打下标记，在后面写上正确的字。 3找出病句。挑出病句划上横线，修改正确。 4标点符号。强调句号、引号、叹号、问号的使用。
5看文章的中心是否鲜明、集中。以上五点是写文章最低的要求。学生经过三四篇文章的批文实践，就能够掌握这几条要求了。修改后，组员再次阅读自己修改后的作文，最后抄写在课堂作文本上。 第三步：各小组互改互评作文 互改互评课上，各小组间交换作文。同样，在组长的带领下，对四本作文进行一一阅读、批改。 1、各小组互改的操作方法： ①格式是否正确。打开作文一看正确，拿出红笔，写上批语，格式正 确；不正确的要批语指出，并修改出正确格式。比如：书信、建议书等等格式。格式不正确扣2分。 ②页面是否整洁。希望学生批改别人作文指出书面不整洁或书写不工 整时，下次自己写作文也要注意，达到自己教育自己的目的。 ③修改错别字。将错字在原文处打下标记，写上正确的字。这样使粗心的同学也认真起来，批改的时候，手里抱着大字典，唯恐漏掉了错别字。发现错别字，每两个扣1分，最多扣5分。10个以上也不再多扣。 ④修改病句或语句不通。挑出病句划上横线，写出病因在何处，再在文中进行修改，每处病句减1分，减至5分，不再多减。 ⑤标点符号有明显错误。强调句号、引号、叹号、问号的使用。明显错误的地方，有一处扣1分，超过5分不再多扣。以上五条在组内时基本就解决完成，小组互换后只是再次检查并作扣分处理，一般经过第一次组内处理都比较好。
3） Attention, please! I’ve something to tell you. Professor Jackson—an English disabled person will come to our school to give us a lecture from 2 to 4 o’clock on the afternoon of April 25 in Room 302, the No. 3 teaching building. His lecture is about how he smoothed away all sorts of difficulties he had met. When he was eight years old, he lost his left leg and right arm in an accident. He struggled in his life and managed to look after himself. He also achieved great success in his work. After the lecture we will have a discussion in groups on how to encourage disabled people, how to help them and how to learn from Professor Jackson. Thank you. 4) Of all the teachers, Mr Moore is the one who impresses me most. Though he is 34, he looks very young for his age. And he’s one of the most popular teachers in our school. Compared with other teachers, Mr Moore pays more attention to his way of teaching. He tries various ways to make his classes lively and interesting. In his opinion, we should not only know “what”, but also understand “why”. So, instead of giving us answers immediately, he encourages us to think by ourselves whenever he puts forward questions. With his help, we’ve learned how to analyze and settle problems. What a wonderful world of “why” he leads us to! He is such a learned person that we all admire him very much. 5） Welcome to our school. I feel it an honour to have the chance to tell you something about our school class. We have one hour activities from 4:20 to 5:20 in the afternoon. Some students read books in the reading room; some have sports on the playground; some sing songs in the theater; some learn to operate computers in the lab and others take part in their group work about different subjects. The majority are most interested in sports and computers. We hope that we can have less homework and moretime to join the activities. We are also looking forward to more visits and tour trips. Thank you. 6）Dear editor, In some places in our country the surroundings is worsening with the air filled with heavy smoke, many mountains turning deserted and rivers polluted. Waste is scattered here and there. So I strongly suggest that the government take effective measures to stop this.
小学生作文批改方法及 步骤 Company number：【WTUT-WT88Y-W8BBGB-BWYTT-19998】
小学生作文批改方法及步骤 第一步：学生自改作文 学生在练习本上写完自己的作文后，自己阅读、修改自己的作文。 但是，学生个人修改，往往“只缘身在此山中”，而且限于水平，文章中的毛病，作者常常自己看不出来。首先要求学生对自己的作文进行复看审核，查找出标点、错别字以及不通顺的句子，并进行改正。接着从题意、中心、内容、感情、结构、语言等方面来一个“回头望”，多问几个“是什么”或“怎么样”，对自己的作文进行从点到面，实事求是的评价。最后，对文章再次阅读，寻找出自己本次作文的最大亮点，或指出今后作文中应该改进的地方，在这样的自我修改，自我反思的过程中，学生的写作能力也在不断提高着。正如叶圣陶先生所说：“批改固教者之要务，然须进一步想，必使学生能自改其文，或文成达而竟不须改，乃有济也。” 第二步：小组内互改作文 组内成员都完成作文后，在组长的带领下，针对每一个组员的作文进行一一的共同阅读，共同修改。修改时要注意： 1格式是否正确。 2找出错别字。将错字在原文处打下标记，在后面写上正确的字。 3找出病句。挑出病句划上横线，修改正确。 4标点符号。强调句号、引号、叹号、问号的使用。 5看文章的中心是否鲜明、集中。 以上五点是写文章最低的要求。学生经过三四篇文章的批文实践，就能够掌握这几条要求了。修改后，组员再次阅读自己修改后的作文，最后抄写在课堂作文本上。 第三步：各小组互改互评作文 互改互评课上，各小组间交换作文。同样，在组长的带领下，对四本作文进行一一阅读、批改。在以前的作文批改中，我首先对所有学生的作文通览一遍，找出其中具有代表性的文章，在作文课上和学生一起进行批改。同时，注意向学生介绍规范性的批改符号，讲解具体的批改方法，从点到面，对典型作文进行全方位的改评。这样做，不但使学生学到了别人作文的长处，起到取长补短，互相促进的作用，而且也使学生学到了作文修改的方法。 1、各小组互改的操作方法： ①格式是否正确。打开作文一看正确，拿出红笔，写上批语，格式正确；不正确的要批语指出，并修改出正确格式。比如：书信、建议书等等格式。格式不正确扣2分。 ②页面是否整洁。希望学生批改别人作文指出书面不整洁或书写不工整时，下次自己写作文也要注意，达到自己教育自己的目的。酌情扣2—3分。
小学生作文的指导方法和要求 以写人物为例说明：（引） 写人，是小学作文训练的基本功之一。在记叙文中，人和事是不可分的，关键是看题目如何要求。要求写事的题目，文中的人要为事服务；要求写人的题目，文中的事必须为人服务。写人为主的记叙文，就是要通过一件或几件事，来表现人物一种或多种品质。写人的继续文，叙事不要求完整；记事的记叙文，虚实要求完整，而且要贯穿文章始终。 （一）通过一件事来写人 通过一件事来写人，通常是表现人物的一种品质或性格的一个方面。为了刻画人物，对所写人物必须进行必要的外貌、语言、动作、心理等方面的描写。但是，从以事写人这个角度来说，最好是选择一件最能反映此人某一特点的事，并把这件事写好。 在写事情的时候，要选择典型的事例。所谓典型，就是能集中反映中心思想的事，能够表现人物的好思想、好品质、美好情感的事。对小学生来说，选择典型事例，要着眼于小事，选择那些最能反映深刻意义的小事。这样的事表面上看，都是普普通通的凡人小事，但是其中却蕴涵着深刻的意义，这就是我们常说的“小中见大”。 （二）通过几件事写人 可以分成两种情况：以是用几件事表现某个人的一种品质；二是用几件事表现某个人的多种品质。 要注意：用几件事写人，这些事可以是完整的，作者必须把事情发生的时间、地点、人物、事件（起因、经过、结果），一一交代清楚，也可以是不完整的，只着重于某几点进行叙述。更多的是在一篇文章中，有的事详写；有的事略写；有的事要求写得比较完整，有的事要求写得比较简单。通过几件事写人，同样要对人物进行必要的外貌、行动、语言、心理的描写。 （三）学会刻画人物 写人的文章要会在叙事的过程中，对最能表现人物思想感情、性格特点的外貌、语言、动作、心理活动等方面进行描写，也就是学会刻画人物。 1.外貌描写 也叫肖像描写，是通过对人物的容貌、神情、衣着、姿态、语调、外貌特征的描写。来揭示人物性格的一种方法。人物的的外貌和人物内心世界密切的联系，具体说：通过外貌描写，使人物的形象更丰满，能给读者留下深刻印象；通过外貌描写，揭示人物的身份；通过外貌描写，展示人物在特定场合的内心世界；通过外貌描写，表现人物性格、精神面貌和思想品质。 总之，外貌描写要和表现人物特点、突出文章的中心思想紧密配合。外貌描写要传神，
中考Composition：一模冲刺作文话题之友情 作文评分标准 中考作文一般从内容、语言、组织结构这三方面进行评分（总分20分）：（一）内容（满分8） 7-8分：内容切题，意思连贯，表达清楚、完整。 5-6分：内容基本切题，意思大致连贯，表达基本清楚、但不够完整。 2-4分：内容不够切题，意思不够连贯，表达不够清楚、有些离题。 0-1分：文不对题，表达不清。 （二）语言（满分8） 词数：每少5个单词扣0.5分，以此类推。只写出个别单词、词不成句不给分。 拼写：每处错误扣0.5分，同一错误不重复计数。 语法：每处错误扣0.5分，同一语法错误不重复扣分。 标点符号、大小写：每两处错误扣0.5分，但扣分总和不超过1分。 （三）组织结构（满分4） 内容充实，上下文连贯，用语规范，表达准确，无语法错误；词汇和句型句式运用恰当，多见好句型和习惯表达用语者，可给3-4分。 内容充实，不写废话，上下文连贯，用语规范，表达准确，无或少见语法错误；词汇和句型句式运用恰当，多见好句型和习惯表达用语者，可给2分。 一般情况下，内容和语言累计得分在15分以上者（含），方可得到1-2分组织结构分。 内容和语言在15分以下者，如文中有值得肯定的好的句型和表达，可酌情考虑给1分组织结构分。 通篇句型句式单一、词汇贫乏者，即使无语法错误，一般也不予给组织结构分。
分类作文提纲 一、话题：友情 二、写作思路及结构： 1. 在审题时，学生要注意描写友情时，内容不能太空洞，而是要通过实例来突出某一项品质，或者对自己的影响等；以及朋友是通过哪些具体的方法帮助自己。 2. 注意使用连接词以及高级词汇，使文章逻辑清晰，内容充实；用具体的实例支撑我的观点。最后进行总结； 3. 围绕友谊可以给出一些建议或者保持友谊的秘诀。 三、高频词：happiness，precious，friendship,colorful, meaningful,problems, comfort, regard, discuss, important,charming, smile, success, confident, responsibility, In my opinion,Independence,brave,encourage, experiences,succeed, difficulties, unforgettable, friendly, suggestions, helpful,understand, unbelievable, disappointed,difficult, boring, improve 四、高频短语：get ready for,learn about, by ourselves, as often as possible, face our future life,give up , make friends, get on well with,make efforts, at that time, believe in themselves, make some mistakes, makegreat progress, try my best to, communicate with, look forwards to, have someproblems with, deal with, stop them from doing it, as soon as possible, have anunforgettable experience, increase our knowledge 五、高频句型：
小学作文修改的步骤及方法 修改作文的步骤及方法 建始县实验小学姜灿俊 指导作文修该是贴近学生习作实际的一次指导。学生是习作讲评的主人。为了发挥学生的主体，增强训练意识, 我尝试了以下教学方法。 一.佳作展示，激发兴趣一一乐评 大教育家孔子说过，'‘知之者不如好之者，好之者不如乐之者。”激发学生的兴趣，是作文教学的良好开端。为了刺激学生的 表达欲望，调动学生参与的积极性，推岀四大版块“榜上有名”"佳作亮相” “片断欣赏” “出谋划策”。在“片断欣赏”让学生有感情 地朗读同学的好词佳句，并配上柔和的音乐，创造一种轻松愉悦 的氛围，也使学生获得成功体验，为习作的讲
评创设良好情境。 二.教师对上次作文的修改进行评价、 1、精选点评，范评引路一一会评 最有价值的知识是方法。为了解决这堂课的重点，让学生掌握如何修改作文的方法，我先选择一篇优秀习作，让学生欣赏、剖析， 并指点写作秘诀。这使得学生在接下来的讲评、修改中有个范本。接着我采用知识迁移的的方法，让学生评析“病”例。有了之 前的佳作范评，学生对“病”文的剖析就能胸有成竹。通过剖析典型作文，使学生知道什么样的作文是佳作，懂得“佳”在何处，“病”文“病”在哪里，更认识到平时要注意观察，展开联想，真情实感，遣词造句才能使作文表达更生动具体。这对学生自我评价习作有很大启发，对学生准确评价自己的习作，恰当修改自己的作文有很强的指导意义。 2、合作评改，培养能力——会改
只评不改的作文讲评课是"纸上谈兵”的空洞说教，只有让学生动手修改习作，学生才会有深切的体会，真正的领悟。叶圣陶先生 说：“教师只给些引导和指点，该怎么改让学生自己去考虑去决定。”于是我给学生创设空间，通过小组合作和集体改文实践，学生 在合作评改中互动交流，互相补充，循序渐进地培养了学生对自己作文进行修改的能力，达到举一反三、触类旁通的目的。 三指导修改教师交代本次作文修改的重点内容，回忆本次作文的要求。指导作文修改： 1、组内评改：可以让学生先说说本次作文的要求，根据习作要求确定评改要点，然后在小组内进行作文评改，并选出组内的优秀作文。 2、全班评改：即“佳作”和“病文”评改。老师选出 、二篇好文章和写得不理想的文章，师生根据本次作文的要求，针对字、词、句等进行逐一评改;
作文的具体步骤及方法 小学生的语言积累还处于初级阶段，如何写作文，如何写好作文成为他们很大的一个障碍，所以如何提高质量成了他们很关注的问题。 一、作文教学的序列目前国内正在实验的作文教学序列，主要有以下三种： (一)以统编教材为基础的作文教学序列 统编教材的作文扣除安排在教材的“基础训练”中，与阅读教学结合穿插进行。一可分三个阶段： 1、一年级.为中年级写片断做准备阶段。通过看图说话、写话、回答问题等形式训练学生说写一句完整的话、几话连贯的话，同时学写请假条、留言条、简单的日记等应用文。 2、三年级，由说话写话向命题作文过渡阶段。要求能写记人记事和状物的简短的记叙文，要求内容具体，条理比较清楚，语句比较通顺，会用标.点，同时学写板报稿、决心书、通知等应用文。 3、四、五年级，命题作文综合训练阶段。进行记叙文写作方法和作文能力的各项训练，使学生作文逐步做到思想健康、中心明确、内容具体、条理清楚、语句通顺。同时进行一般书信、读书笔记、会议记录等应用文教学。 (二)以景山学校实验教材为基础的作文教学序列 该校实行“读写结合，以作文为中心安排语文教学”，以名家名篇为典范，严格进行写作训练。 一、二年级在集中大量识字的同时，突出字词句的训练进行大量造句、抄书、听写句子和段落、看图写诗写片断、写日记等练习。同时引导学生留心观察和反映周围的人、本、秆境，养成观察习惯，积累写作素材。这样，到二年级下学期，“绝大多数学生就能在教师指导下，写出三、四百字的短文，为下一段作文启蒙打好基础。 三年级是作文启蒙阶段。主要采取“放胆文”的形式，把文章“写开”、“写顺”。从三年级下学期起，就指导学生围绕中，用逻辑思维去选择和组织生活中那些生动、形象、具体的材料，要使文章内容具体，叙述细致生动。 四年级是掌握规律，严格训练阶段，教会学生如何写人、记事、状物等。 五年级是运用规律，提高作文水平阶段，训练学生能写出夹叙夹议央抒情的儿童小品。
修改作文的步骤与方法 第一步是过判断关，就是在通读文章的基础上，对主题（中心）是否突出，观点（态度）是否鲜明，所选材料是否典型，结构是否合理，层次是否清楚，详略是否得当六个方面作出判断，对要修改的文章获得总体认识；第二步是过推敲关，就是在确认文章总体框架的基础上对字、词、句、标点符号的运用作出推敲，进行修改；第三步是过润色关，就是对通过修改后的文章，再作润色。只要教师不厌其烦地强调修改步骤，学生修改作文的良好习惯就会迅速形成，修改能力也就会很快提高。 无论选用哪种方法，均须从两个大的方面去努力。①是指导学生以多角度多层次多方位的思维观去思考修改的重点与方法。②是指导学生脚踏实地地进行逐字、逐词、逐句、逐层的分析修改。这样指导，不仅使学生在修改中懂得了修改方法的取舍，而且学会了运用作文批改术语评点修改作文的方法。 第一步：符号示意法。所谓符号示意法，就是教师在浏览学生作文时，遵循着正确的衡文标准，顺手划下符号，以符号指导学生修改。 这种批改方法，既可以把教师从繁琐的作文批改中解放出来，又可以引导学生自己动手修改文章。 第二步：自改自评法。自改中，学生感到最困难的是：将内容进一步深化。这是学生修改中的障碍，教师在眉批中要善于提出问题，解开结症，插上路标，在他们感知、感受的基础上加以感情的点化，使他们再回到经历过的事件中去，再体验、再消化，以至在认识上迅速得到突破，主题自然地得到升华。 文章自改后，再仔细阅读品味，并写下只言片语的感受，即自评。这种自评不要求全面，只要求真切，防止自评流于形式，或成为学生写作的累赘。 第三步：自评自讲法。学生自改自评后的文章交给教师，教师根据学生的自改自评情况，选出典型，当面加以辅导，让受辅导者在班上作自评自讲。这样不仅提高了该生对作文的认识，培养了口头表达能力，强化了写作兴趣，而且也交流了写作与修改的经验，同学们听来感到亲切，易于接受。与此同时，将产生一种羡慕感、追求感。 学生的自改、自评、自讲的过程，是学生作文逐渐自我完善的过程，教师要把握这一过程的规律，认真培养学生自改自评的习惯，提高学生自改的能力，使他们的文章逐渐达到“理真情切而意达”的境地。
八年级英语上册作文复习资料 1.有很多同学早晨上学不吃早餐，这是一个不好的习惯，对身体有很大的危害。请根据提示写一篇短文，指出不吃早餐的危害。提示1.不吃早餐对身体有害 2.不吃早餐会影响上午听课。 Every morning, we have to go to school very early, so many of us don?t have breakfast. It?s very bad for our health. In the morning we usually have four clas ses. It?s a long time before lunch. If we don?t eat anything for breakfast, we may feel hungry and we can?t listen to the teacher carefully. We need energy very much while we are growing. I really think that we should have a good breakfast. 2 . How to keep healthy If we want to keep our bodies healthy, we must have a good habit. We should get up and go to bed early and sleep at least eight hours every day. Do more exercise, such as walking, swimming, playing balls and so on. We should also eat healthy food—more fruit and vegetables and less meat. If you don?t feel well, you?d better see a doctor at once. And we should wash our hands before meals and drink enough boiled water every day. It?s necessary for our health. We should not throw litter about, keep long fingernails and smoke etc. It?s also very important. 3. 从饮食，睡眠和运动几方面谈谈怎样可以保持身体健康。
My favourite city My favorite city is Beijing, the capital of our country.It is in the north of China. There are more than 15 million people in Beijing, which makes the city crowded. I like eating dumplings and ducks there because they’re
very delicious. If you go to Beijing, you can visit many museums, palaces and parks there. In a word, Beijing is the most attractive city in my eye. My favorite indoor activity Of all the indoor activities,doing some
reading is my favorite. ( My favorite is doing sth.) I have got a habit of reading almost every evening before going to bed. ( I am used to reading something for 30 minutes). In my view, reading can not only enrich my knowledge, but also broaden my
作文审题步骤及方法 一、复旧导入 上节课我们了解了作文训练一般包括五种能力的训练，看看同学们还记得吗？ 学生回答。 对。有审题能力、立意能力、谋篇能力、表现能力、修辞能力。(ppt展示) 今天我们主要是进行审题能力的训练。 作文审题分标题式命题作文审题、情景式命题作文审题、话题式作文审题、材料式命题作文命题、综合式作文审题。（课件展示） 今天，我们就进行标题式命题作文审题能力的训练。（出示课件）。 标题式作文的审题，看似容易，其实要真正正确、准确、明确地弄清题意，并非易事。因为文章的命题越具体，限制就必然越多越死。题中无闲字。如果一个字，一个词忽略了，弄错了，势必造成不同程度的文不对题，“偏离题意”，甚至“严重偏离题意”。那要怎样才能正确、准确、明确地分析题意呢？ 二、展示本节课的任务和目的 通过教学，了解命题式作文的审题方法，会审题，写一篇完整的文章。 三、授课过程 （一）知识汇集。 审题定义：审，审查，了解，斟酌，审题即写文章前仔细了解题目的含义、要求。 审题，是作文的第一步。 （二）、审题方法知识解析 第一步：审命题的标题。 1、单词类。 相对说，这类命题比较好审，只要咬文嚼字弄清词语的含义就可以了。 例如：98年全国高考作文《习惯》，什么是“习惯”，词典的释义说：“习惯是指在长时期逐渐养成的，一时不容易改变的行为、倾向和社会风尚”。根据这一解释考虑，无论写一个人的某种爱好、习性，还是一个地区、一个名族、一个国家的某种传统作法、认识、习俗，都符合题意。 应该注意的是，除了词的本义，还要想到它的引申义或比喻义，也就是我们平时所说的弦外之意。 例如：《绿叶》《桥》《春风》等一些题目的比喻义远远大于词义的本身，以《春风》为例，它就是借用“春风送暖”的特性，给处于困难、危难之中的人或事送去的关爱、呵护、帮助。不能单纯地谈自然界之风，就偏离了题意。 2、短语类。 这类命题大致有偏正、动宾、并列几种。 ①偏正结构，关键词多在偏的部分。如：《绿色的童年》，“童年”是思考的关键， 选取事件一定得是童年，然后再考虑事件的性质必须是“绿色”的，也就是说必 须是具有生命力旺盛、健康、纯净等特点。 ②动宾结构。其关键词多是动词。如《改造我们的学习》，题旨就是“改造”，而“学 习”是改造的对象，。 ③并列结构。如：《索取与奉献》，重点在让我们阐述人生的意义在于奉献而不是索 取，绝不能单纯的议论什么是“索取”、什么是“奉献”。再如，《勤奋和成功》 是因果关系，《知识与能力》是相关关系，《欢乐与痛苦》是相反关系，《自尊与 自强》是递进关系，只要抓住了这种关系及转化，就是抓住了主题。 3、句子类，这类题目一般是一个比较复杂的句子。审题时要抓住主谓部分的中心词或者
Composition – description 1. 描写人物外貌和性格特征的常用词语： tall 高的，short 矮的，fat 胖的，thin瘦的，black/ blond hair 黑色的、金色的头发, big / bright eyes 大大的、明亮的眼睛，b rave 勇敢的，beautiful 美丽的，clever 机警的，ugly丑陋的，lovely可爱的，talkative健谈的，easy-going好相处的，angrily生气的， sad 难过的，happy 高兴的，excited 兴奋的，pleased 高兴的，satisfied 满意的，angry 生气的，worried 担心的，disappointed 失望的，terrified 恐惧的， friendly 友好的，smart 伶俐的，polite礼貌的， friendly友好的，foolish愚蠢的，cute可爱的，one-year-old一岁大的， be like grapes像葡萄一样的，hard-working勤劳的， honest诚实的， anxious 焦虑的，eager急切的，good-looking 长得好看的 ugly-looking 长得难看的 wise 明智的，funny-looking 长相滑稽的 ordinary-looking 长相一般的lazy 懒惰的white-haired 白头发的 warm-hearted 热心肠的healthy 健康的kind-hearted 好心的 absent-minded 心不在焉的diligent 勤奋的bad-tempered 脾气不好的 near-sighted 近视眼的far-sighted 远视眼的 pretty 漂亮的naughty 淘气 的curious 好奇的，easy-going 温和宽容的 lovely 可爱的 bright 聪明的humorous 幽默的 funny 滑稽的silent 沉默的attractive 有吸引力的 杏眼：almond-shaped ，小而亮的眼睛：beadlike ，美丽的: b eautiful ，大的: big/large 明亮的: bright ，眼珠突出的: bulging ，离的很近的: close-set ，深陷的: deep-socketed/deep-sunken ，梦幻般的: dreamy ， 呆滞的: glazed，柔和的: gentle ，呆板的: fishlike ， 凹陷的: hollow/sunken ，远视的: longsighted/farsighted ，近视的：myopic/shortsighted ，眼梢上斜的: oblique ，老花眼的: presbyopic，圆的: round ， 性感的: sexy ，锐利的: sharp ，斜的: slanting ， 细长的: slitty ，小的: small/tiny ，明亮的: starry，水汪汪的: watery， 分的很开的: wide-spaced ，肿胀的：swollen，水灵灵的: dewy ， 斜视眼的: squint， 2. 日常活动： have/ take a bath 洗澡，make the bed 整理床铺，take photos拍照， keep quiet保持安静，kick shuttlecock t踢毽子，skip跳绳， play with 玩耍，have interest in= be interested in 对。。。感兴趣， be tired of 对。。。感到厌倦、厌烦，grow up长大， make friends 交朋友，play the piano弹钢琴，go shopping逛街，购物，chat on line上网聊天，listen to music 听音乐，be fond of 喜欢， play computer games玩电脑游戏，hate 憎恨 be crazy about 对------极度喜欢enjoy 喜欢， lose interest in 对------失去兴趣
How Do students Spend Their Summer Vacations In the past, summer vacations meant an escape from the academic life and a restoration to freedom. Most students enjoyed their rights of leisure to the ultimate extent. Summer vacation were made up of endless activities such as visiting friends, watching TV, fishing, touring and occasional help of housework of chores. However, the trend has changed. Currently, students are fully occupied during the summer vacation. Some are busy attending various skill training courses, trying to obtain a driving license, pass language competence tests, or challenge computer qualification tests, while others are busy seeking part-time jobs to experience an adult world. On the whole, they want to be well equipped for students to accumulate enough skills and experiences for a bright prospect but leisure-time cannot be ignored, even be omitted. Therefore, we’d better arrange summer vacations in a more flexible way. Recreation Recreations are an important part of people’s life. For example, after hours of attentive study, students feel like having a football game to relax their nerves. Workers, too, find it very satisfying to sit in front of a TV set for an hour or two when they come back from a day’s tiring work. Besides, recreations serve as a pleasing way for the retired people to pass their excessive time. Everywhere you go, you will find that during their spare time, people are engaged in recreational activities of one kind or another. Generally speaking, there are two kinds of recreations: physical activities and intellectual activities. Physical activities, on the one hand, keep one fit and develop team spirit. Basketball is a n example. On the other hand, intellectual activities such as playing chess and reading novels can train one’s brains and provide temporary escape from one’s troubles. In my opinion, there should be a balance between the two forms of activities. This is because physical activities are necessary for good health while intellectual activities are beneficial to one’s mind. Therefore, in order to make his life enjoyable, one should go in for both kinds of pastimes. A Letter to Harvard University and Apply for Administration into the MBA Program Dear Sirs, I graduated two years ago from the Department of International Trade at the University of International Business and Economics, the leading institution of business education in the people' s Republic of China. I am now applying for admission into the MBA program of your university next fall, that is, after I finish three years of being an employee in the branch company of SONY in Beijing. It is my great pleasure to have taken international trade as my major as China is expanding its trade with foreign countries. I earnestly hope I will have an opportunity to pursue graduate study at Harvard University which has a high reputation for its business education. My TOEFL score is 650 and GRE is 2038. Please send me an application form and information regarding your scholarships and assistantships.
作文修改的方法与形式 A【方法】 一、【减分法】 要求学生从以下10个方面着手修改作文，每个方面最多扣五分。 1.格式是否正确。比如：标题是否写在第一行正中，每段开头是否空2格，是否分小段来写，应用文自身的格式遵守没有。如果格式不正确，酌情扣分。 2.卷面是否整洁。比如书写是否工整、规范，文面是否清楚、干净，有无涂抹，有无巫巴，有无破损。如果文面不整洁，酌情扣分。 3.错别字几个。发现错别字，要将错别字在原处打上叉叉，改正过来，并且写到批语中。每个错别字扣一分，本项最多扣五分。 4.有几处病句。凡病句，都要在下面画上横线，写出病因是什么，再在后面批语中，写清病句几处。每个减一分，本项最多扣五分。 5.标点符号有几处错误。发现标点符号有明显错误的地方，改正过来，一处扣一分，超出五处，不再多扣。 6.看文章的中心是否鲜明，集中。中心鲜明是说，作者赞成什么，反对什么，应该旗帜鲜明，不要模楞两可。中心集中是说，一篇文章只有一个中心，不能多中心。中心不集中通常表现在：①扣题不紧；②偏题，离题，跑题；③笔墨不集中，行文过散；④思路不明确，内容前后衔接不紧密。如果中心不鲜明，集中，酌情扣分。 7.看表达方式。主要看其是否符合文章体裁的要求，记叙文以记叙为主，说明文以说明为主，议论文以议论为主。一篇文章应该有明确的体裁，不能写成这也不像，那也不像的东西。（除此之外，还要看其是否符合作文指导的要求。）如果表达方式不符合文体要求，酌情扣分。 8.看文章的选材。这条批语提三点要求：⑴选材是否围绕中心。⑵选材是否符合生活实际。 ⑶选材是否具有典型性。 9.看文章的结构。也提三点要求：⑴层次段落是否清晰。⑵过渡是否自然。⑶开头和结尾是否照应。 10．看语言是否简练，通顺，准确。语言不简练，重复罗嗦，酌情扣分。语言不通顺，不是指有病句，而是指句与句之间衔接不连贯，也酌情扣分。 二、【三过目修改法】 “三过目”修改法：第一遍以最快速度浏览全文，了解文章全貌，边看边找出错别字。第二遍逐句逐段仔细修改，写上眉批、旁批。第三遍以一目十行的速度扫视一遍，检查批阅情况，写好总评。 三、【欣赏式批改法】 除指出作文中明显的错误外，着重仔细寻找作文中的亮点，进行表扬。 B【形式】 一、自改：学生完成作文后，随即自己进行修改。一般用“三过目修改法”和“减分法”。 二、互改：同组对子间互相交换作文修改。一般用“欣赏法”和“减分法”。 三、组改：同组学生一般以3人小组（abc搭配）为单位，一位书写好的学生执笔，另两名学生参与讨论，共同完成对3篇作文的修改。一般采用“减分法”和“欣赏法”。 C【注意】 1、修改的过程也是学习研究和再创作的过程，务必认真仔细，努力提高自己的写作水平。 2、要有改动的痕迹，比如：“错别字”打上叉叉，病句下面画横线，多余的词句用删除号，补充的词句用补充号。要有旁批或眉批，总评。