WO2002094927A1

WO2002094927A1 - Stabilized citrate-plasticized flexible pvc

Info

Publication number: WO2002094927A1
Application number: PCT/EP2002/005206
Authority: WO
Inventors: Karl-Josef Kuhn
Original assignee: Crompton Vinyl Additives GmbH
Current assignee: Galata Chemicals GmbH
Priority date: 2001-05-18
Filing date: 2002-05-11
Publication date: 2002-11-28
Anticipated expiration: 2003-11-18

Abstract

By using a perchlorate and a terminal epoxc compound, a high stabilization of citrate-plasticized flexible PVC is achieved

Description

Stabilized Citrate-Plasticized Flexible PVC

The present invention relates to flexible PVC (polyvinyl chloride) stabilized by epoxy compounds and perchlorates using citrate plasticizers, a process for its preparation, and its use.

PVC can be stabilized by a number of additives. Heavy-metal compounds of lead and cadmium are particularly suitable, but are objectionable today for ecological reasons due to their heavy metal content (cf. "Plastics Additives", R. Gachter and H. Mϋller (editors), Hanser Verlag, Munich, Vienna, New York, 3rd edition, 1990, pages 287-295, and Kunststoff Handbuch PVC, Volumes 1 and 2, Beck/Braun, Carl Hanser Verlag, Munich).

Epoxy compounds have long been known as co-stabilizers for PVC. Epoxidized soybean oil is frequently used (cf., for example, "Plastics Additives", R. Gachter and H. Mϋller (editors), Hanser Verlag, 3rd edition, 1990, pages 303/4, and US-3,928,267). For chlorinated polyvinyl chloride, the use of glycidyl ethers of novolak resins as stabilizers is also described, for example, in DE-A-34 02 408 and EP-A-0 677 551 and EP- A-0 677 550. DE 35 46 725 C2 relates to polyvinyl chloride compositions comprising citrate esters as plasticizers, and a process for its preparation. These respectively contain Ca/Zn stabilizers.

It has been the object of the present invention to provide new plasticizers for PVC. According to the invention, the above object is achieved by a flexible PVC containing

a) citric acid esters of general formula I

R_aO-C(COOR)(CH₂-COOR)₂ I

wherein

R respectively represents a straight- or branched-chain alkyl residue having from 4 to 18 carbon atoms, and R_a represents H or CH3-CO-.

b) at least one perchlorate compound of formula M(CIO₄)_n, wherein M represents H, Na, K, Mg, Ca, Ba or Al, and n corresponds to the valence of M;

c) a terminal epoxy compound containing an epoxy residue of formula II

wherein

Ri and R₃ are hydrogen;

R₂ is hydrogen or methyl, and n equals 0; or

Ri and R₃ together form -CH₂-CH₂- or -CH₂~CH₂-CH₂-, R₂ is hydrogen, and n is 0 or 1; the epoxy residue being directly bound to a carbon, oxygen, nitrogen or sulfur atom.

Further, it may also contain additional organic or inorganic zinc compounds and/or tin compounds, such as Zn stearate, Zn oleate, Zn octoate, Zn acetate, Zn citrate, ZnCI₂ and/or dimethyl-, dibutyl-, dioctyl-, didodecyltin thioglycolates or tin carboxylates.

The Japanese unexamined Patent Publication JP Hei 3-122149 proposes a rigid PVC composition which contains solid epoxides and perchlorates.

It has now been found that citrate-plasticized flexible PVC stabilized by a mixture of a perchlorate and a terminal epoxide has an excellent thermal stability with a good initial color and color preservation. Surprisingly, the citrate-plasticized flexible PVC stabilized according to the invention meets the high requirements which are met, for example, by PVC stabilized with barium/zinc compounds. It is to be pointed out that excellent storage stability and light stability are achieved. Further, a good stabilization is achieved independently of the state of aggregation of the epoxide, i.e., liquid terminal epoxides may also be employed without disadvantage.

As compared to usually employed phthalate plasticizers, a citrate plasticizer can often be used in a reduced quantity while the properties of the plasticized polymer remain comparable.

Preferably, the flexible PVC according to the invention does not contain any lead or cadmium compounds. As used herein, "flexible PVC" means PVC mixtures which contain at least one citrate plasticizer in an amount sufficient to achieve properties of flexible PVC.

PVC having a freezing temperature of more than 70 °C is not considered a flexible PVC according to the invention.

Further, flexible PVC according to the invention is defined by being suitable for the preparation of flexible PVC molded parts due to its plasticizer content. These include, in particular, cable and wire coatings, roof sheets, book sheets, decorative sheets, foams, agrarian sheets, office sheets, automotive sheets (also foam-backed with polyurethane), flexible tubes, sealing profiles and the like.

Also suitable as a PVC component for the compositions according to the invention are blends, copolymers or graft polymers of PVC with polymerizable compounds, such as acrylonitrile, vinyl acetate, or (co)polymers such as ABS, which may be suspension, bulk or emulsion polymers and their mixtures. Examples of such components (a) include compositions comprising (i) from 20 to 80 weight parts of a vinyl chloride homopolymer (PVC), and (ii) from 80 to 20 weight parts of at least one thermoplastic copolymer based on styrene and acrylonitrile, especially selected from the group consisting of ABS, NBR, NAR, SAN and EVA. The abbreviations used for the copolymers are familiar to the skilled person and have the following meanings: ABS: acrylonitrile-butadiene-styrene; SAN: styrene-acrylonitrile; NBR: acrylonitrile-butadiene; NAR: acrylonitrile-acrylate; EVA: ethylene-vinyl acetate. In particular, acrylate- based styrene-acrylonitrile copolymers (ASA) may also be used. In the composition according to the invention, one or more of the mentioned copolymers may be present. Of particular importance is flexible PVC which contains (i) 100 weight parts of PVC and (ii from 0 to 300 weight parts of ABS and/or SAN- modified ABS, and from 0 to 80 weight parts of the copolymers NBR, NAR and/or EVA, but especially EVA, and from 3 to 60 weight parts of citrate plasticizer per 100 weight parts of (i) and (ii).

As the alcohol component of the citric acid ester, there are preferably employed C4-C14 alkanols which may be branched or unbranched and whose alkanol residues may be the same or different, linear ones being particularly preferred.

Further, mixtures of different plasticizers may also be used. As such mixtures of plasticizers, there may be used, in particular, those disclosed, for example, in EP-A-0 677 551, which is included herein by reference.

Such additional plasticizers include, for example, phthalic acid esters, esters of aliphatic dicarboxylic acids, trimellitic acid esters, epoxy plasticizers, polymer plasticizers, phosphoric acid esters, chlorinated hydrocarbons, and paraffins, hydrocarbons, monoesters, glycol esters as mentioned in EP 0 677 551 or in "Plastics Additives", R. Gachter and H. Mϋller (editors), Hanser Verlag, 1990, page 284, chapters 5.9.14.2 and 5.9.14.1, and "PVC Technology", W.V. Titow (editor), 4th edition, Elsevier Publishers, 1984, pages 171-173, chapter 6.10.2, page 174, chapter 6.10.5, page 173, chapter 6.10.3, and pages 173-174, chapter 6.10.4. Perchlorates

The perchlorates mentioned above as component (b) correspond to the formula M(CIO₄)_n, wherein M represents H, Na, K, Mg, Ca, Ba or Al, and n corresponds to the valence of M.

The respective perchlorate may be employed in different usual dosage forms, for example, as a salt or aqueous or organic solution, or charged onto a carrier material, such as PVC, Ca silicate, chalk, zeolites or hyd rota I cites, or incorporated into a hydrotalcite by a chemical reaction, or dissolved in the plasticizer itself.

They may be employed in an amount of, for example, from 0.001 to 5, conveniently from 0.01 to 3, more preferably from 0.01 to 2.0 weight parts, based on 100 weight parts of PVC.

Epoxy compounds

The terminal epoxy compounds (c) which can be used according to the invention may have an aliphatic, aromatic, cycloaliphatic, araliphatic or heterocyclic structure; they contain epoxy groups as pendant groups. The epoxy groups are preferably linked to the residual molecule as glycidyl groups through ether or ester linkages, or they are N-glycidyl derivatives of heterocyclic amines, amides or imides. Epoxy compounds of these types are generally known and commercially available.

The epoxy compounds contain at least one epoxy residue of formula II

wherein Ri and R₃ are both hydrogen, R₂ is hydrogen or methyl, and n equals 0; or wherein Ri and R₃ together form -CH₂-CH₂- or -CH₂-CH₂- CH₂-, R₂ is hydrogen, and n is 0 or 1; the epoxy residue being directly bound to a carbon, oxygen, nitrogen or sulfur atom. Such epoxy compounds are known to the skilled person from EP 0 506 617 A, which is included herein by reference.

The citrate-plasticized flexible PVC stabilized according to the invention may contain further additives. These include, for example, fillers and reinforcing agents (such as calcium carbonate, silicates, glass fibers, talcum, china clay, chalk, mica, metal oxides and hydroxides, carbon black or graphite), metal soaps (such as zinc octoate/stearate or calcium stearate) and other metal stabilizers (dialkyltin thioglycolates or dialkyltin carboxylates, for example, T22, 17MOK, T9, T4 or T7, all of which are products of the Crompton Vinyl Additives GmbH), antioxidants, polyols, zeolites, dawsonites, hydrotalcites, organic phosphites, 1,3-diketo compounds, dihydropyridines, phenylindoles, pyrroles, β-naphthol, hydroxydiphenylamines, sterically hindered amines (HALS), light- stabilizers, UV absorbers, lubricants, fatty acid esters, paraffins, blowing agents, optical brighteners, pigments, flameproofing agents, antistatic agents, β-aminocrotonates, phosphates, thiophosphates, gelling aids, peroxide scavengers, modifiers and other complexing agents for Lewis acids. Such further additives are extensively set forth in EP-A-0 677 550, EP-A- 0 677 551 and EP-A-0 465 405, page 6, lines 9-14, which are included herein by reference.

A survey of usual metal soaps can be found in Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, vol. A16 (1985), pages 361ff, which is included herein by reference.

Further illustrations relating to the useful and preferred aluminum compounds can be found in US-4,060,512 A and US-3,243,394 A, which are included herein by reference.

Further preferred rare-earth compounds can be found in EP-A-0 108 023, which is included herein by reference.

Optionally, a mixture of zinc, tin, alkaline earth, aluminum, lanthanum or lanthanoide compounds of different structures may be employed. Also, organic zinc, tin, aluminum, lanthanum or lanthanoide compounds may be coated onto a support, such as alumosalt compounds; see also DE-A- 40 31 818, which is included herein by reference.

Suitable organotin compounds are described in US 4,743,640 (columns 3-5), which is included herein by reference.

Preferred is a stabilized citrate-plasticized flexible PVC containing from 0.001 to 5.0 parts per 100 parts of PVC of a perchlorate or perchloric acid, and from 0.1 to 50 parts per 100 parts of PVC of a terminal epoxy compound, and optionally an antioxidant, especially from 0.01 to 10.0 parts per 100 parts of PVC. Further preferred is a stabilized citrate-plasticized flexible PVC containing an alkali metal perchlorate as component (b).

Further preferred is a stabilized citrate-plasticized flexible PVC containing a terminal epoxy compound comprising an aromatic group, especially a bisphenol derivative, as component (c).

Further, particularly preferred is a stabilized citrate-plasticized flexible PVC containing (b) from 0.001 to 3.0 parts per 100 parts of PVC of a perchlorate, and (c) from 0.1 to 5.0 parts per 100 parts of PVC of a terminal epoxy resin.

Further preferred is a stabilized citrate-plasticized flexible PVC which additionally contains pigments and/or fillers, especially chalk.

Further preferred is a stabilized citrate-plasticized flexible PVC which additionally contains one or more metal soaps, especially zinc soaps.

Further preferred is a stabilized citrate-plasticized flexible PVC which has been foamed by chemical or mechanical blowing agents and additionally contains several metal soaps, especially zinc soaps.

Further preferred is a stabilized citrate-plasticized flexible PVC which additionally contains at least one additive selected from the group consisting of disaccharide alcόfϊols, organic phosphites, zeolites, hydrotalcites, dawsonites, aminocrotonates, polyols, diketones, pyrroles, β-naphthol or dihydropyridines. Further preferred is a stabilized citrate-plasticized flexible PVC which additionally contains a sterically hindered amine, especially from 0.01 to 5 parts per 100 parts of PVC.

Further preferred is a stabilized citrate-plasticized flexible PVC which optionally contains an organic or inorganic Zn compound, such as Zn stearate, Zn oleate, Zn octoate, Zn acetate, Zn citrate and/or ZnCI₂.

Further preferred is a stabilized citrate-plasticized flexible PVC which optionally contains an organic tin compound, such as dialkyltin carboxylates or dialkyltin thioglycolates.

According to the invention, the perchlorates or perchloric acids are preferably employed in combination with a terminal epoxy compound for stabilizing PVC. To the individual stabilizers and the PVC itself, the above illustrated preferences apply, and also, one of the above described further components may be additionally employed.

The citrate-plasticized flexible PVC stabilized according to the invention can be prepared in a per se known manner by mixing the stabilizers mentioned and optionally further additives with the PVC using per se known devices, such as calenders, mixers, kneaders, extruders, dissolvers and the like. The stabilizers may be added singly or in admixture, or also in the form of so-called master batches. Thus, the invention also relates to a process for the preparation of stabilized citrate-plasticized flexible PVC, characterized by mixing components (b) and (c) and optionally further additives with the PVC using devices such as calenders, mixers, kneaders, extruders, dissolvers and the like. The citrate-plasticized flexible PVC stabilized according to the invention can be formed into the desired shape in a per se known manner. Such methods include, for example, milling, calendering, extruding, injection- molding, sintering or spinning, and also extrusion-blowing or processing by the plastisol method. The stabilized citrate-plasticized flexible PVC can also be processed into foams.

The citrate-plasticized flexible PVC stabilized according to the invention is particularly suitable for flexible formulations, especially in the form of wire coatings, cable insulations, decorative sheets, foams, agrarian sheets, flexible tubes, sealing profiles and office sheets, and for automotive applications.

The following Examples further illustrate the invention without being limitative in any way. As in the rest of the description, parts and percentages are by weight, unless otherwise specified.

Examples:

A citrate-plasticized flexible PVC composition was prepared by mixing the individual components according to the following Tables (quantities stated in weight parts).

The components (PVC powder, plasticizer, stabilizer mixture, additives etc.) were homogenized using a plastisol mixer (dissolver) for about 3 minutes and coated onto release liner using a coating knife to give 0.5 mm thick films, and gelled to solid sheets in a Mathis oven at 190 °C for 3 min. These were subjected to a static heat test or other methods for determining thermal stability in the known manner.

The determination of long-term stability was effected by a static heat test according to DIN 53381, wherein the specimen was stored in a test oven at 190 °C, and the time it took for the sample to become black was determined.

Another determination of long-term stability ("VDE test") was effected by establishing the thermal stability according to DIN VDE 0472. Thus, the specimen was placed into a glass tube sealed at the bottom (AR glass supplied by Peco-Laborbedarf GmbH, Darmstadt), heated in an oil bath at 200 °C, and the time was determined at which a visible reddening (corresponding to a pH value of 3) of the pH universal indicator paper was observed.

Another determination of the stability of the PVC is effected by the dehydrochlorination test ("DHC test"), performed by analogy with DIN 53381, sheet 3. Thus, the time until the dehydrochlorination curve began to rise was measured at the respectively stated temperature.

Long-term oven storage test

PVC sheets of dimensions 10 x 10 x 2 mm were prepared. Then, they were stored in an oven at a defined temperature of between 100 and 132 °C (± 0.5 °C) for a respectively defined time (3, 7, 14 days), and their consistency was determined, or they were subjected to the above described dehydrochlorination test. Permanent rolling test

The PVC mixture was rolled at a temperature of 180 °C on a rolling mill having a gap width of 0.5 mm, and every 5 minutes, a sample was taken, and its yellowness index, YI, was measured after cooling.

Table I:

Dehydrochlorination test at 190 °C

^1} Linplast^® 68 CT, supplied by Condea, ²⁾ diisononyl phthalate, ³⁾ bisphenol-A diglycidyl ether (Araldit^® GY 250, supplied by Ciba)

It was found that the stabilization with epoxide and perchlorate (mixture) according to the invention was far superior to that with epoxidized soybean oil and perchlorate, and no effect of destabilization with NaCIO₄ was seen, and that an unexpectedly better thermal stability as compared to phthalate (DINP) was obtained. Table II:

Static heat test at 190 °C

* Yellowness index after (5) min and after (15) min, lower values = good color

¹⁵ Linplast^® 68 CT (linear 6,8-alcohol citrate ester),

³⁾ bisphenol-A diglycidyl ether (Araldit^® GY 250) ^u) Ca stearate and Loxiol^® G 71 S (1: 1), ¹²⁾ low-viscous bisphenol-F glycidyl ether

A good stabilization with different, also liquid, epoxides was found. Surprisingly, the addition of Zn soaps did not result in any noticeable destabilization, while the addition of epoxide with NaCIO₄ resulted in sufficient stabilization. Table III:

Static heat test at 190 °C

Rough sheet at 180 °C, rolled for 5 min, 0.5 mm thickness

^la) Citrate plasticizer supplied by Condea; linear 8,6-alcohol citrate ester;

³⁾ bisphenol-A diglycidyl ether (Araldit^® GY 250)

⁶⁾ Zeolite A supplied by Degussa; ⁷⁾ hydrotalcite supplied by Kyowa;

* supplied by Giulini; ** octyltin stabilizer of Crompton Vinyl Additives

GmbH The positive effect of inorganic co-stabilizers and the color-improving influence of tin stabilizers could be observed.

Table IV:

Static heat test at 190 °C

^la) Citrate plasticizer supplied by Condea;

²⁾ bisphenol-A diglycidyl ether (Araldit^® GY 250); ⁹⁾ stearoylbenzoylmethane;

¹⁰⁾ complex ester wax; ¹⁵⁾ solid heterocyclic epoxy resin (triglycidyl isocyanurate);

* octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate There could be observed: a) the positive effect of phenolic antioxidants (AO), and b) the superiority of the mixture according to the invention over the corresponding mixture comprising epoxidized soybean oil.

Table V:

Permanent rolling test at 180 °C

YI = yellowness index (= degree of discoloration); the lower the YI, the higher is the heat stability

^1} Citrate plasticizer supplied by Condea; ²⁾ bisphenol-A diglycidyl ether

(Araldit^® GY 250); ⁹⁾ stearoylbenzylmethane; ¹⁰⁾ polyethylene wax;

¹⁵⁾ solid heterocyclic epoxy resin (triglycidyl isocyanurate), supplied by

Ciba. In this test too, the mixtures comprising terminal epoxide were superior to those comprising epoxidized soybean oil, and the synergistic effect with perchlorates was also shown.

Claims

C L A I M S:

1. A flexible PVC containing

a) citric acid esters of general formula I

R_aO-C(COOR)(CH₂-COOR)₂ I

wherein

R respectively represents a straight- or branched-chain alkyl residue having from 4 to 18 carbon atoms, and Ra represents H or CH₃-CO-.

c) a terminal epoxy compound containing an epoxy residue of formula II

wherein

Ri and R₃ are hydrogen;

R₂ is hydrogen or methyl, and n equals 0; or

Ri and R₃ together form -CH₂-CH₂- or -CH₂-CH₂-CH₂-, R₂ is hydrogen, and n is 0 or 1; the epoxy residue being directly bound to a carbon, oxygen, nitrogen or sulfur atom.

2. The flexible PVC according to claim 1, characterized in that R represents an alkyl residue having from 6 to 14 carbon atoms.

3. The flexible PVC according to claim 1, characterized in that R represents a linear alkyl residue having from 4 to 14 carbon atoms.

4. The flexible PVC according to claim 1, characterized in that component (b) comprises an alkali metal perchlorate.

5. The flexible PVC according to claim 1, characterized in that component (b) comprises a perchlorate compound in a concentration of from 0.01 to 1.0 phr.

6. The flexible PVC according to claim 1, characterized in that component (c) comprises a terminal epoxide compound with an aromatic group, especially a bisphenol derivative.

7. The flexible PVC according to claim 1, containing at least one or more substances selected from the group consisting of fillers and reinforcing agents, metal soaps and other metal stabilizers, antioxidants, polyols, zeolites, dawsonites, hydrotalcites, organic phosphites, 1,3-diketo compounds, dihydropyridines, phenylindoles, pyrroles, β-naphthol, hydroxydiphenylamines, sterically hindered amines (HALS), light-stabilizers, UV absorbers, lubricants, fatty acid esters, paraffins, blowing agents, optical brighteners, pigments, flameproofing agents, antistatic agents, β- aminocrotonates, phosphates, thiophosphates, gelling aids, peroxide scavengers, modifiers and other complexing agents for Lewis acids.

8. The flexible PVC according to claim 1, additionally containing a phenolic antioxidant.

9. The flexible PVC according to claim 1, additionally containing fillers, especially chalk, and pigments, especially titanium dioxide.

10. The flexible PVC according to claim 1, additionally containing one or more metal soaps, especially zinc soaps, or organic alkyltin mercapto compounds or carboxylates.

11. The flexible PVC according to claim 1, additionally containing one or more organic or inorganic zinc compounds and/or tin compounds, especially Zn stearate, Zn oleate, Zn octoate, Zn acetate, Zn citrate, ZnCI₂ and/or dimethyl-, dibutyl-, dioctyl-, didodecyltin glycolates or tin carboxylates, each of them especially in an amount of from 0.01 to 5 phr.

12. A process for the preparation of flexible PVC according to any of claims 1 to 11, characterized by mixing components (a), (b) or (c) together with PVC in plastisol coating plants, calenders, mixers, kneaders, extruders or dissolvers.

13. Use of flexible PVC according to any of claims 1 to 11 for preparing molded parts and utility articles.

14. The use according to claim 13 for the preparation of automotive sheets, wire coatings, decorative sheets, foams, agrarian and food sheets, flexible tubes, sealing profiles, office sheets or foamed sealing sheets, extruded profiles or articles of flexible PVC.