CA1069643A

CA1069643A - Impact-resistant polyvinyl chloride based on ethylene-vinyl acetate and ethylene-alkyl acrylate copolymers

Info

Publication number: CA1069643A
Application number: CA226,406A
Authority: CA
Inventors: Robert Buning; Franz Blaschke; Werner Trautvetter
Original assignee: Dynamit Nobel AG
Current assignee: Dynamit Nobel AG
Priority date: 1974-05-07
Filing date: 1975-05-06
Publication date: 1980-01-08
Also published as: SE7505235L; SE411455B; BE828724A; DE2421900A1; JPS5123559A; DE2421900B2; FR2270294A1; NL7505396A; FR2270294B1; GB1510537A; NO751570L; IT1044327B

Abstract

ABSTRACT OF THE DISCLOSURE:

Impact - resistant polyvinyl chloride compositions, based on ethylene - vinyl acetate or ethylene - alkyl acrylate copolymers. These are formed by a polymer mixture of (a) 4 to 15% by weight of a graft polymer, containing an ethylene copolymer with 2.5 to 15% by weight of copolymerised vinyl acetate or alkyl acrylate as the base polymer and 5 to 70% by weight of vinyl chloride grafted onto the copolymer in the gel phase, (b) up to 96% by weight of polyvinyl chloride and/or vinyl chloride copolymers and (c) conventional additives. The PVC compositions of the invention have improved U-notched impact strength; they are particularly suitable for use as weather-resisting materials.

Description

-'~ 1069t~43 The present invention i3 concerned with impact-resistant polyvinyl chloride based on ethylene-vinyl acetate and ethylene-alkyl acrylate copolymers. -~
It is known that copolymers of ethylene and vinyl acetate (E-VA) are components in~trumental in imparting impact strength to PVC. The effect of E-VA copolymers in imparting im-pact strength to PVC i8 governed both by the vinyl acetate content of the copolymer and by its molecular weight (D. Hardt in Br.
Polym. J. 1969, Vol. 1, September, pages 225 - 232). ~he E-VA
copolymers must have a minimum molecular weight in excess of about 5000 if they are to be effective in imparting impact strength.
; ~owever, it is the vinyl acetate content of the E-VA
copolgmer which i8 of crucial significance 80 far as impact strength and, in particular, U-notched impact strength are concerned.
The optimum value is obtained with copolymers having a ~inyl acetate content of 45 ~ by weight.
Below and above thi8 vinyl acetate (VA) content of 45 %, the PVC thus compounded shows far weaker U-notched impact strengths.
With ~inyl acetate contents of 28 and 65 % by weight, standardised to equal additions of the E-VA copolymer, the U-notched impact 8trength (according to DIN 53 453) only just exceeds the value for PV~. Wibh VA content~ of less than 20 % by weight, the U-notched impact strength o~ pure PVC is not improved, whilst its notched impact strength may even fall below the minimum permitted levels.
~ ardt attributed the need for the dependence indicated above to ¦~ ~ the physical properties and, in particular, to the elastic charac-: ter of the ~-VA copolymers in dependence upon their VA-content.
Similar observations have also been made in regard to the effeot of ethylene-alkyl acr~late copolymers and their acry-c~ ~30 ~ late~conten~ in imparting impact ~tren~th. Even graft polymers ofvinyl ohloride on the above-mentioned E-VA copolymers remarkably show the ~ame properties with a pronounced optimum of elasticisa-,,~ : '' 1CH~ 4 3 tion, as reflected in particular in U-notched impact strength, at Va content~ of approximately 45 % by weight in the E-V~ graft ba~e of the graft polymer~.
In contrast to these findings from the prior art, it has now been found that graft polymers of vinyl chloride grafted onto ~-VA copolymers with low and very low VA- contents a~d onto cor-responding ethylene-acrylate copolymers, impart a high level of elasticity to PVC-More particularly, it has been found that ethylene-vinyl acetate copolymers and ethylene-acrylate copolymers with a high ethyle~e content, for example between 97.5 and 85 % by weight, have an outstanding effect in imparting impact strength to PV~
providing they are grafted in the gel phase with vinyl chloride.
By carrying out the graft copolymerisation reaction in this way, the vinyl chloride together with the catalyst enter~
the copolymer without dissolving it and is graft-copolymerised in the solid phase with the copolymers.
The present invention relates to impact-resistant poly-vlnyl ¢hloride based on ethylene-vinyl acetate or ethylene-alkyl a¢rylate copolymers, characterized by a polymex mixture of 4 to ; ~ 15 % by weight of a graft polymer, containing an ethylene copolymer with 2.5 to 15 % by weight of copolymerised vinyl acetate or alkyl acrylate a3 the base polymer and 5 to 70 % by weight of ~in~1 chloride grafted onto the copolymer in the gel phase, up '~ to 96 % by weight of polyvinyl chloride and/or vinyl chloride oopolymers and the usual additive~.
i ~ The copolymers used in accordance with the invention, name}y ethylene-vinyl acetate or ethylene-alkyl acrylate, should have ~rom 5 to 70 % by weight of vinyl chloride and preferably 30~ ; from 10 to 60 % by weight of VA grafted onto them. In admi~ture !, with Pva~ these graft copolymers form impact-resistant PVC-composi-tions. The impact strength of these PVC compo~itions 18 governed '

- 2 -.

10~;9t~43 both by the quantity and type (chlorine content, molecular weight) of the graft polymer used and by the processing conditions. In order to obtain high impact strengths, especially below room tem-perature, i.e. at low temperatures, the graft polymer has to be used in qua~tities of from 4 to 15 % by weight. In general, ~uantities of from 5 to ~2 ~ by weight give good re~ults.
In cases where the mixture contains VC copolymers instead of or in addition to the PV~, these ~C-copolymers may be the usual VC-copolymers processed into moulding compo~itions in which usually up to about 15 % by weight and, in ~ome cases, up to about 40 % by weight of a monoethylenic monomer has been copolymerised with vinyl chloride. The graft polymer and PVC are processed together with additives by compounding to form a polymer mlxture or so-called "compound". ~he quantity of PVC and additive~
together make up the quantity of the graft polymers to 100 % by .Yeight, although the additives do not exceed small, standard quan-tities ln the range from about 2 % by weight to a maximum of 10 by weight. In special cases, these tried and tested additives, ~uch as lubricants and heat or decomposition stabilisers, W -sta-bilisers, which are required partly for facilitating processingand partly for finishing the product or which are desirable from case to oase, may even be supplemented by other additives, such a~ small qua~tities of active fillers.
~ he processing conditions under which the compound is produced and processed have to meet certain requirements, as known per ~e. During "mixing" of the conætituents in the softened, thermoplas~ic state, for example on a roll at temperatureæ in the range ~rom about 150 to about 195C, it iæ important to avoid both inhomogeneity through too few rolling operations, inade~uate rol-ling times and inadequate temperature9 and also the danger ofndead rolling" through exceæsively long and overintensive mixing or d~mage attributable to excessively high temperatureæ. ~he :

~ - 3 -, . --~069643 ~ame applies to subsequent processing of the rough sheet, for example by re-rolling, pressing, etc. ~he best values for impact and U-notched impact strength and other mechanical properties may be determined by testing using the methods normally adopted by experts, although they may be derived from the ~xamples reported herein. ~actor~ requiring particular consideration in this res-pect are the quantity and chlorine content of the graft polymer.
In general, increasing addition~ of the graft polymer necessitate higher processing temperatures, whilst increaæing chlorine con-tents, i.e. increasing quantities of the VC grafted on, necessi-tate lower processing temperatures.
Production of the graft polymers may be carried out relati~ely easily because the readily grindable ethylene copoly-mers can be ground at room temperature into powders which are direotly added to the polymerisation mixture before the beginning Or graft polymerisation. Grafting in the gel phase eliminates the need for the time-consuming dissolution of the base poly~er in the monomeric VC which is a requirement of numerous graft polymerisation reactions.
One particular advantage of grafting in the gel phase i~ that the ethylene copolymers with their high ethylene content, generally amounting to approximately 85 % by weight, which are usually producéd by high-pressure polymerisation are readily I obtainable and do not ha~e a viscous/tacky consi~tency which seriously complicates the handling of numerous ethylene copolymers euch as E-VA copolymers with low ethylene contents, for example of the order of 50 %.
The molecular weights of the ethylene copolymers shou~d be in the range from 5000 to 150,000 and are correspondingly increa~ed in dependence upen the quantity of VC grafted on.
, ~ ~he graft polymerisation reaction carried out in thegel phase i5 di~tinguished by the fact that both the ba~e polymer ~ . ~ ... .. . . .

1069t~43 and also the graft polymer produced are always present in the solid phase. ~he vinyl chloride is grafted on by introducing monomeric VC together with the cataly~t into the base polymer followed by polymerisation. These then are the condition~ under - which polymerisation i~ carried out. ~he monomer is generally grafted directly onto the E-VA granulate in the absence of any further aids, the only components present in the polymerisation autoclave, providing the high-te~perature polymerisation reaction is carried out at suitable temperatures, being the base polymer, VC and a catalyst solublè therein, i.e. ~oluble in organic phase, similar to the conditions under which bulk polymerisation reactions are normally carried out, In addition to the above-mentioned component~, however, it is also possible to add water, emulsifiers, suspension stabi-lisers, small quantities of organic solvents, optionally regula-tors~ etc. Suitable catalysts are, for example, dialkyl peroxides 8uch as dilauroyl peroxide or dicyclohexyl peroxide, azo compounds such a~ azoisobutyronitrile or even the peroxy dicarbonates used in the u~ual quantities. Favourable graft polymeri~atio~ veloci-ties are obtained with these catalysts at temperatures in the rangefrom 30 to about 90C.
It i8 best to use ~uitable stirrers, such as spiral agitator~ or wall-sweeping stirrers and shearing stirrers.
In cases where copolymers of ethylene and alkyl acryla-te~ are used as the base polymer, it i5 preferred to use those with C1 to a8 alkyl group~, both of the linear and branched type, of which butyl acrylate, the ethylbutyl acrylates and ethylhexyl acrylates are mentioned.
~ The graft polymers thus produced are highly compatible - 30 with PVC of a variety of different make~ a~d with the usual K-values, 80 that it is e~en po~sible if desiTed satisfactorily to work additions of more than 15 % into PVC. Remarkably, it is .
' - ~ , :

10~i9~i43 only the graft polymer~ which are effective in imparting impact strength, tAe base polymers present in them being ineffective on their own, as demonstrated for comparison in the ~amples reported herein by U-notched impact strengths in the range from 2 to 4 kp/cm2 which indicate inadequate elasticisation, i.e. inadequate impact strength, of the PVC both in connection with measured impact etrength values of "broken"(g) and "intact" (i.t. i.e. above ~50 kp/cm2).
It has also surprisingly been found that an adequate activity level of the graft polymer~ is linked to an upper limit of the ethylene content in the base polymer of about 97 or 97.5 %
by weight.
As shown by Comparison Example 12, a gra~t po~ymer based on a polyethylene (~upolen; trademark) produced by corres-pon~ing high-pre~sure polymerisation remains inadequate in its elasticising and strengthening effect for only moderate notched lmpa¢t ~trength and, in some cases, even deteriorated, other mechanical value~, as does the ungrafted polyethglene of Compari-~on Example 11.
~he production of the graft polymers in the gel phase wlll now be further understood with re~erence to the following -~ -non-restrictive Examples, and a¢comp~nying ~ables.
~he Exa~ples relating to the impact-resistant polyvin~l chloride are followed by Comparison Examples in which equal addi-tions of the corresponding ethylene copolymer used as base for the graft copolymers, recognisable from the ~ame VA-content, were used .
In the ~ables, thesecond column indicates this VA-cont~ent in the base polymer of the graft polymers and in the copolymer used for the Comparison Examples.
~he third column indicates the chlorine content of the graft polymers, expressed by the quantity of VC gra~ted on9 chlorine - :

10696~3 .
contents of the order of 14 % corresponding to a ~uantity of approximately 25 % by weight, and chlorine contents of the order of 28.5 % to a qua~tity of approximately 50 ~ by weight of PVC
grafted on in the graft polymer. -EXAMP~E A
Production of a graft polymer based on an ethylene-vinyl -acetate co~polymer with a vinyl acetate content of 7.5 % by weight and a molecular weight of 26000 (as measured by osmometry in o-dichlorobenzene at 85C):
3300 g of granulated copolymer, Alkathene*VJ~ 502 (a product of ICI), and 21 g of dilauroyl peroxide are introduced into a 30 litre steel autoclave flushed wlth nitrogen and equipped with a wall-sweeping spiral agitator. ~he spiral agitator is set to rotate at 100 rpm, whilst the temperature i~ adjusted to 60C.
After a reaction time of 2 hours, the temperature is reduced to 40C and, a~er another 15 minutes,the excess vinyl chloride is blown off. 4.4 kg of a graft copolymer with a Cl content of 13.8 % by weight are obtained.
~he OE aft polymer is soluble in warm tetrahydrofuran, in other words it is uncros~linked. It has a molecular weight of approximately 55 000. No vinyl chloride homopolymer can be detected in the graft polymer.
A similar result is obtained by using an E-VA copolymer ~:! with a vinyl acetate content of 3 % by weight (~upolen V 2524 EX, l .- .
-~ a product of ~ASF) or an E-VA copolymer with a vinyl acetate -content of 13 % by weight (~upolen V 3510 K, a product of BASF) as graft base, or by using 3300 g of a copolymer of 97 % by weight of ethylene and 3 % by weight of n-butyl acrylate.
Graft polymers with chlorine contents of about 13.4 to 14.0 % by weight are obtained u~der the conditions and with the quantities indicated above, corresponding to grafted-on vinyl chloride contents of approximately 25 % by weight.
* Trademark ,l.. , .; . - - .

- . .: . ~ . . . .. . ..

EXAMP~E B
Production of a graft copolymer with a high PVC content:
402 cc o~ desalted water, 38 cc of 3 % by weight aqueous methyl cellulo~e, 99 g of E-vA copolymer with a copolymerised ~inyl acetate content of 7.5 % by weight (in powder form, obtained by grinding the granulate in the cold), 121 g of vinyl chloride and 0.85 g of dilauroyl peroxide, are introduced into a 1 litre glass autoclave equipped with a ~piral agitator after the air present has been di~placed by nitrogen. ~he temperature i~
adjusted to 55C. After a polymerisation time of 5 hour~, 198 g of powder-form graft copolymer are obtained with a chlorine content of 28.4 % by weight, corresponding to a grafted-on vinyl chloride content of the order of 50 % by weight.
EXAMP~E ~
Production of impact-resistant PVC sheet based on EVA-~inyl chloride graft polymers with 13 % of VAc in the EVA copoly-mer and grafted with vinyl chloride in the gel phase, Cl-value 13.8 (acoording to Example A):
270 g of PVC of the suspension type with a K-~alue of 68 (dry-blend type), 30 e of E-VA graft polymer, 6 g of stabiliser ~7 N (dibutyl tin mercaptide) and 1.5....of E-wax (low molecular ', weight polyethylene3, are proce~sed on a roll for ~5 minute~ at a temperature of 180C to form a rough sheet. While it is still hot, the rough sheet i~ pressed for 4 minutes at a temperature of 185C to form a 4 mm thick pres~ed sheet. Standard bars are ~awn rom the 4 mm sheet and used to mea~ure impact ~trength and U-notched impact strength in accordance with DI~ 53 453.
~ he ~alues for ~rafted and ungrafted material are ¦~ ~ set out in Iable 1.
~30 1~

,,~.

. - . - : . - . , . .- . .. .

lO~g~43 '~able 1 Addition U-notched impact strength impact strength kp/cm kp/cm2 10 % by weight of grafted E-VA 35.5 i.t.
10 % by weight of E-VA (comparison) 3.8 b.
~he grafted material produces a considerable improvement in the mecha~ical properties of the polyvinyl chloride. ~his is surprising and could not have been predicted from previous expe-rience. ~he mechanical properties and measured values quoted are governed not only by the composition of the graft polymer but also by the processing condition~, especially the processing temperature.
Ungrafted material, in the present case the copolymer of r ethylene a~d 13 % by weight of vinyl acetate, adversely affects the mechani¢al properties when added to PVC. During processing it accumulates at the æurface and results in blocking and smearing of the roll and pres~.
~he compari~on material is neither impact resistant nor usable in any way. ¦~-EXAMP~ES 2 to 12 Sheet material containing 10 ~ by weight of graft poly-mers of different compositions in PVC (K-~alue 68) i8 produced in accordance with Example 1. ~able 2 shows the U-notched impact ~trengths and impact strengths in dependence upon ~he roll and press temperatures, the VAc-content of the E-VA polymers and in dependence upon the chlorine content of the graft polymer. ~or ~ ¦
comparison, the particular E-VA copolymer is also quoted in 10 %
~30 by weight compounding with the same PVC.
i~ ~he molecular weightq of the graft polymer~ used are ~;in the range from 20 000 to 60 000.
., .
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-` 10~9t;43 The rolling conditions correspond to those of Example 1 in regard to the rolling time of about 15 minutes, but on this occasion only those rolling temperatures (temperature of the rolls) and press temperatureæ which led to the best properties of the products, especially the highest U-notched impact strengthæ, are quoted.

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_ 10696~3 It can be seen from Table 2 that, by graft polymerisa-tion in the gel phase, E-VA copolym,ers of low VA content (even as low as, for example, 3 ~ by weight) become component~ effective in imparting impact strength to PVC. If the VA-content is zero, i.e. in the ca~e of polyethylene or its graftpolymer~, this effect i8 only obtained to a limited extent.
EXAMP~ES 13 to 21 Sheet material i8 produced a~ in Example 1 from 7 % by weight of a graft copolymer of vinyl chloride on an ethylene-n-butyl acrylate copolymer (molecular weights 25 000 to 65 000). ~he results are set out in ~able 3.
Table 3 Example Acrylate ~ Cl Roll Press U-notch Impact (% by weight) temp. temp. 2 strength C C~ kp/cm kp/cm2 . .
13 14.0 o.O 170 17l5 3.5 i.t.
(comparison) 14 14.0 14 1 170 175 38.6 i.t.
14.0 28.1 170 170 28.5 i.t.
16 6.5 0.0 175 180 3.2 b.
(oomparison) .
17 6.5 14.0 175 180 35.6 i.t.
18 6.5 26.8 170 175 28.6 i.t.
19 3.0 o.o 180- 185 1.6 b.
(oomparison)

3.0 13.8 180 185 35.8 i.t.
, 21 3.0 27.8 175 180 25.6 i.t.
Table 3 shows that graft polymers of copolymers with aorylates have advantages over those with vinyl acetate (cf. ~a- -ble 2). On the other hand, they ha~e an improved re~istance to weathering in relation to graft copolymers of ethylene copoly-;30 mers with vinyl acetate contents.
Corresponding results are obtained with copolymers of ;~ ethyl-n-hexyl acrylate.

~ ' -

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Impact-resistant polyvinyl chloride compositions characterised by a polymer mixture of a) 4 to 15% by weight of a graft polymer, containing an ethylene copolymer with 2.5 to 15% by weight of copolymerised vinyl acetate or alkyl acrylate as the base polymer and 5 to 70%
by weight of vinyl chloride grafted onto the copolymer in the gel phase, b) up to 96% by weight of polyvinyl chloride or vinyl chloride copolymers, or both, and c) conventional additives.

2. Compositions according to claim 1, wherein the graft polymer is present in an amount of from 5 to 12% by weight.

3. Compositions according to claims 1 or 2, wherein the graft polymer contains from 10 to 60% by weight of vinyl chloride.

4. Compositions according to claim 1, wherein the ethy-lene copolymer has a molecular weight of from 5,000 to 15,000.

5. Compositions according to claims 1 or 4, wherein the copolymerised alkyl acrylate contains linear or branched chain alkyl groups having from 1 to 8 carbon atoms.

6. Compositions according to claim 1, wherein the ad-ditives are present in an amount of from 2 to 10% by weight.

7. Compositions according to claims 1 or 6, wherein the additives are selected from the group comprising lubricants, decomposition stabilizers, UV-stabilisers and active fillers.