DD300977A7 - Process for the preparation of carboxylated ethylene-vinyl acetate copolymers - Google Patents

Abstract

Carboxylated EVAC products for use as an adherent coating material or impact-resistant component for thermoplastics are prepared by free-radical (co) graft polymerization of monoethylenically unsaturated monocarboxylic acids, in particular acrylic acid (AS), and dicarboxylic acids or their anhydrides, in particular maleic anhydride (MSA), on EVAC a vinyl acetate content of between 5 and 25% (EVAC-5/25) using organic peroxidic or diazo group-containing initiators, in particular dialkyl peroxydicarbonates having a 10-hour half-life (10h-HWZ) between 40 and 45 degrees C or diacyl peroxides with a 10 h HWZ (0.1M benzene solution) between 60 and 75 degrees C, in a monomeric mass concentration of between 5 and 50% and maintaining a dry powdery to granular consistency of the polymerization medium at polymerization temperatures between 30 and 100 degrees C. The monomer (s) en) AS, MSA or AS / MSA mixtures with mass Ratios between 5/1 and 1/1 are used taking account of a monomer conversion of between 60 and 98% in amounts corresponding to the concentration of carboxyl groups to be set between 2 and 70 g per kg of EVAC-5/25.

Description

With regard to grafting of ethylenically unsaturated monocarboxylic or dicarboxylic acids, the latter preferably in the form of their acid anhydrides, on polyolefin backbone chains, including EVAC with a VAC content that can be varied within wide limits between 5 and 70%, basically two methods are known: once those below ^100.degree C in an organic Lösungsmittl and on the other hand at higher temperatures (140-250 ° C) in an extruder odor melt kneader carried out graft polymerization.

Radical grafting of carboxyl-containing monomers onto ethylene polymers, including EVAC ₁ in an organic solvent (DE 2420942, DE 2329780, JAP 15422/69), gives modified copolymers having an increased adhesiveness. In this case, the Klobofähigkeit of the EVAC used as the backbone polymer (VAC-Antoil between 5 and 70%, preferably from 10 to 40%, selectable) by using further polar comonomers, in particular VC and optionally vinyl ester in admixture with acrylic acid (AS) and / or maleic anhydride (MSA), to be further improved (DE 2329780).

However, such a process carried out in a larger amount of a solvent, irrespective of the complicated course of the reaction, is due to long reaction times and the overall complicated polymer insulation.

Finally, solvent separation and recovery, not economically viable.

The practically simpler modification of polyolefins by radical grafting of ethylenically unsaturated compounds containing carboxyl groups is based on a reaction in the melt, using a kneader or extruder (US 3,177,269, US 3,172,770, US 3,579,476, US 3,987,122, DE 1694126, DE 1720256, DE 2342486, JAP 6384/64). By various technological and procedural variations occurring disadvantages may be accompanied with respect to the insufficient monomer conversion and at high temperatures in the range between 150 and 25O ⁰ C to be listed crosslinking reactions of the polyolefinic material, including a sharp drop in the melt index and a limited adhesive strength, or occurring Molemassenabbau, which leads to a deterioration of the mechanical-physical level' avoided.

Thus, by using small concentrations of unsaturated carboxylic acids (AS) or anhydrides of dicarboxylic acids (MSA) with intensive premixing in the extruder, an almost complete monomer conversion is achieved (DE 2242324). The same result is obtained for much higher monomer concentrations when MSA is cotopolypolymerized in admixture with styrene or with AS (US 3579476).

Not to be excluded at the high polymerization temperatures in the melt and the resulting short reaction times between about 5 and 30 minutes is the formation of a high proportion of homopolymers of the ethylenically unsaturated carboxylic acids (anhydrides). Although the structurally inhomogeneous graft product mixtures structurally in this way can be used for various fields of application because of their overall improved adhesion, they on the other hand have only partially sufficient mechanical-physical characteristics.

A targeted improvement in terms of increased grafting yield of the monomeric AS or methacrylic acid (MAS) can be achieved if the ethylenically unsaturated carboxylic acid which contains the radical peroxidic or diazo-containing initiator dissolved in the EVAC granules before the start of the melt grafting (DE 2342486). Despite the technological measures mentioned, it is not completely possible to prevent the degradation of the molecular weight of the EVAC during its modification in the melt and thus a drop in the mechanical characteristic level. In addition, the extruder parts, which come in contact with the corrosive monomers at the high temperatures, have to meet extremely high material property requirements, which leads to a considerable increase in costs.

Object of the invention

The object of the invention is the economical production of carboxylated EVAC with increased adhesion strength and improved mechanical-physical properties.

Explanation of the essence of the invention

The invention has for its object to provide a process for the preparation of carboxylated EVAC by free radical grafting monoethylenically unsaturated mono- and dicarboxylic acids or their anhydrides on EVAC with a mass fraction of copolymerized VAC units between 5 and 25% (EVAC-5/25) Use of organic peroxidic or diazo group-containing initiators at temperatures between 30 and 100 ⁰ C and maintaining a dry powdery to granular consistency of the polymerization, ie excluding water and any organic solvents, dispersants or diluents, for use as adhesion-resistant coating materials or in thermoplastic

To develop molding compounds for improving their impact strength.

According to the invention the object is achieved in that the monomer corresponding to a concentration of carboxyl groups between 2 and 70g per kg EVAC-5/25 and the initiator in a concentration between 5 and 50%, based on the submitted

Monomer composition used and until zj a monomer conversion between 60 and 98% is polymerized.

Acrylic acid (AS) and maleic anhydride (MSA) are used as preferred monomers.

The use of AS / MSA mixtures in a mass ratio between 5/1 and 1/1 leads to the expected

Modification of the submitted backbone polymer.

As an initiator is preferably a known compound from the series of Dialkylperoxidicarbonate with a 10-Stunaen half-life (10-h HWT, measured in 0.1 m Benzenlösungl between 40 and 45 ⁰ C or diacyl peroxides with a 10-h HWT between 60 and 75 ⁰ C in a concentration of 10 to 40%, based on the submitted monomer composition used.

The preferred EVAC 5/25 backbone polymers have the most important characteristics:

Degree of crystallinity from 0.3 to 0.5 (i.e., in general proportions of 30-50% by volume of crystalline PE)

- Density ρ (according to TGL 14075) between 0.915 and O ^ Og / cm ³

- average particle diameter C _m between 0.05 and 0.5mm

Melt Index MFI ° ₂ ° (after TGL25244) between 0.1 and 10 g / 10 min

- Number average molecular weight ^ _n between 15,000 and 40,000 as well

mass average molecular weight M "between 100,000 and 200,000.

The dispersion of the reaction components, d. H. the distribution of the monomer (s) and initiator (s) on the backbone polymer surface does not require any special (additional) technically complex measures. It takes place essentially in a process stage upstream of the polymerization stage at room temperature and is continued or completed in the heating phase until the start of the polymerization. The Gosamtprozeß can be carried out in various reactors, which in addition to conventional "non-pressurized" mixing devices especially horizontal stirred reactors for in powdery (granular) medium using specific Tempcratur-Time Programr * * -u successive Prozauschführung (dispersion, grafting reaction, product discharge, including Compared to solution and especially melt grafting, the process according to the invention is distinguished by a significantly greater range of variations in terms of the graft polymerization conditions and thus also of the "settable" polymer structures (which can be identified, inter alia, by such characteristic values as carboxyl group concentration, gel content and melt index). , It is characteristic that compared to the graft products prepared in a homogeneous phase, which generally have negligibly small gel contents and significantly higher melt indices, the products of the invention depending on the choice of the individual polymerization parameters, specifically shown in the following embodiment, for consistently low flowability full spectrum of possible gel contents (criterion for heterogeneous grafted products). It is surprising that these modified EVAC-15 products, despite their higher to very high gel contents and low melt indices, can be incorporated well into thormoplastic materials and are equipped with a high impact strength.

The adhesive strength on a metal or Thermoplastunterl'age is mainly dependent only on the carboxyl group concentration [-COOHI.

embodiment

In a temperature-controlled and equipped with a wall-mounted stirrer horizontal reactor is submitted EVAC with the following characteristics;

EVAC 15 EVAC 18 C _n , 0.25 mm 0.30 mm VAC content 15.3% 18.2% M "/ M _w 13000/141000 29200/177000 MFI ¹⁹⁰ ° ^C MFI _212n 3.6 g / 10 min 1.87 g / 10 min P 0.932 g / cm ³ 0.937 g / cm ³

The reaction procedure is described in detail with reference to the experiment listed in Table 1 under no. 9: To 100 parts by mass (MT) of EVAC-15 10MT AS are added together with 1 MT dilauroyl peroxide (DLPO) and stirred at room temperature with stirring over a period of Dispersed for 30 minutes. Thereafter, the reaction is carried out according to a predetermined temperature (T) time (t) program

t (min) 0 30 60 90 120 150 180mm. T ( ⁰ C) 30 38 42 54 62 66 7O ⁰ C,

wherein, after reaching the polymerization end temperature Tp _n of 70 ° C in total for a period of t _Pm = 120min at constant Tp _n , polymerized. Thereafter, the reactor contents are cooled and purged with nitrogen before at room temperature (reactor temperature about 3O ⁰ C) ( "shell-free") in total 109.2 MT white product from the polymer feed free reactor are discharged

 As characteristic parameters are determined:

- Carboxylgruppengehaltl-COOH] 4.53% (determined by titration), based on total graft product mass

- Gel mass fraction m.gtoreq.48.80% (solution residue of a product quantity of 2 g, in 100 ml of xylene, after 12 h treatment under reflux)

- MFI] ⁹⁰ ₂ ^OC j 0,16g / 10min

Based on the breadth of variation of the process of the invention, in particular with respect to the backbone polymer properties (using EVAC-15 and EVAC-18 above), the concentrations of monomers (AS and MSA) and initiators corresponding to the chosen temperature regime (besides DLPO with a 100 h -HWZ of 62 ⁰ C further dibenzoyl peroxide, DBPO, with a 10-h HWZ of 72 "C and Diisopropylperoxidicarbonat, DIPP, with a 10-h HWZ of 44 ⁰ C) are prepared by the same technology further graft polymerization.

For comparison, some analogous composite melt graft products (using, inter alia, an EVAC backbone polymer with 35% VAC, MFI of 2.8g / 10min (EVAC-35) and di-t-butyl peroxide, t-BP, with a 10h HWZ of 124 ⁰ C indicated as an initiator

 Table 1 shows the results.

Documents considered: DE-OS 2023154 DE-OS 2450672

Table 1

Ser. No. Backbone polymer ICO MT graft polymerization Initiator (MT) (H) ^T p _m Graft-characteristics " ¹ GeI _MFI 190 ⁰ C (g / 10 min) 1 EVAC 15 Grafting 0.5 DLPO 3.1 70 £ COOH] 38.2 0.15 Vgl.l EVAC 15 2.5 AS 0.1 t-BP 0.2 190 1.01 1.3 4.4 2 EVAC 18 2.5 AS 1.0 DLPO 3.2 70 0.95 65.2 n.m. 3 EVAC 18 2.5 AS 0.5 DLrO 3 / 1.5 70 1.19 37.0 0.19 Vgl.3 EVAC 35 5.0 AS 0.1 t-BP 0.2 200 2.62 1.2 9.8 4 EVAC 15 5.0 AS 0.1 DLPO 3 / 0.5 70 2-, 34 20.6 2.1 Vgl.4 EVAC 35 0.5 AS 0.02 t-BP 0.15 190 0.26 0.2 18.5 5 EVAC 18 0.5 AS 1.0 DIP 3.2 50 0.27 46.5 0.06 6 EVAC 18 5.0 AS 0.5 DBPO 3.1 80 2.41 72.0 0.03 7 EVAC 18 5.0 AS 1.0 DBPO 3 / 1.5 80 2.70 74.1 n.m. 8th EVAC 18 5.0 AS 1.0 DLPO 3.2 70 2.22 69.7 η. m .. Vgl.8 EVAC 35 7.5 MSA 0.2 t-BP 0.2 185 4.12 1.8 10.2 9 EVAC 15 7.5 AS 1.0 DLPO 3.2 70 3.58 48.8 0.16 Vgl.9 EVAC 15 10.0 AS 0.2 t-BP 0.2 200 4.53 2.7 11.7 10.0 AS 4.36

Continuation Table 1

Ser. No. Backbone polymer 100 MT graft polymerization Initiator (MT) t ^{1} t} Pm (h) ^T Pm (° c) Pfrcpfprodukt characteristic values " ¹ GeI (%) _MFT 190 ⁰ C MFI _{212 N} (g / 10 min) 10 EVAC 18 Grafting (MT) 0.5 DLPO 2.5 / 1 70 [-cooh] (%) 13.2 2.67 Vgl.10 EVAC 35 2.5 MSA 0.2 t-BP 0.2 165 2.80 0.0 8.77 11 EVAC 18 2.5 MSA 1.0 DLPO 3 / 1.5 70 2.50 52.0 0.44 12 EVAC 15 2.5 MSA 1.0 DLPO 3 / 1.5 70 1.64 55.7 C, l 13 EVAC 18 2.5 MSA 0.5 DIP 3 / 1.5 50 2.24 1.6 3.61 Vg1.14 EVAC 35 1.5 MSA 0; 02 t-BP 0.1 200 1.05 0.0 12.8 15 EVAC 18 0.3 MSA 1.0 DIP 3.2 50 0.22 1.84 2.1 16 EVAC 18 2.5 MSA 0.5 DBPO 2.1 80 2.0 93.7 0.78 17 EVAC 15 2.5 MSA 1.0 DLPO 3.2 70 1.91 52.1 n.m. 18 EVAC 18 (1.7 MSA (3.3 AS 1.0 DLPO 3.2 70 3.12 66.5 η. iQ. (2.5 MSA (5.0 AS 3.97

n.m. - not measurable

Number: heating time from 30 ⁰ C to T

pm

Second number: Polymerization time at constant T _pm

co ο

Claims (5)

1. A process for the preparation of carboxylated ethylene-vinyl acetate copolymers by free-radical graft polymerization of monoethylenically unsaturated mono- and dicarboxylic acids or their anhydrides on ethylene-vinyl acetate copolymers having a mass fraction of copolymerized vinyl acetate units between 5 and 25% (EVAC-5/25 ) using organic peroxidic or diazo group-containing initiators in the temperature range between 38 ⁰ C and 100 ⁰ C while maintaining a dry powdery to granular consistency of the polymerization medium for use as adhesion-resistant coating materials or as schlcgzhöherhöhen addition in thermoplastic molding compositions, characterized in that the monomer accordingly a concentration of carboxyl groups between 2 and 70g per kg of EVAC-5/25 and the initiator in a concentration between 5 and 50%, based on the submitted Monom ^ rmasse, used and up to a monomer conversion between 60 and 98% polymer is isiert. 2. The method according to claim!, Characterized in that is used as the monomer acrylic acid (AS). 3. The method according to claim 1, characterized in that maleic anhydride (MSA) is used as the monomer. 4. The method according to claim 1, characterized in that an AS / MSA mixture is used in a mass ratio between 5/1 and 1/1. 5. The method according to claim 1 to 4, characterized in that the initiator is a known compound from the series of Dialkylperoxidicarbonate with a 10-hour half-life (measured in 0.1 m benzene solution) between 40 and 45 ⁰ C or the diacyl peroxides with a 10-hour half-life between 60 and 75 ° C in a concentration of 10 to 40%, based on the monomer composition presented, is used. For this purpose 2 pages tables Field of application of the invention The invention relates to a process for the preparation of carboxylated ethylene-vinyl acetate copolymers by radical grafting of monoethylenically unsaturated mono- and dicarboxylic acids or their anhydrides on ethylene-vinyl acetate copolymers of the composition corresponding to 5 to 25g copolymerized vinyl acetate (VAC) units per 100g copolymer at temperatures between 30 and 100 ⁰ C and using organic perodix or diazogruppenhaltiger initiators - with the exclusion of water as a dispersion, suspension or emulsion medium and organic solvents - for use as adhesion-resistant coating materials or as impact modifiers in various thermoplastic molding compositions. Characteristic of the known state of the art It is known to chemically modify EVAC for use as an impact modifier, but also as an adhesion-resistant film or coating material in various ways. The most important method is the grafting of various, depending on the intended use selected ethylenic unsaturated, mostly polar compounds on the EVAC Backbone. The applied graft polymerization method is based on the one hand on the specific composition, the structural parameters and physical characteristics of the EVAC and on the other hand on the specific nature of the modification, d. H. especially according to the monomer or monomer mixture to be used and the concentrations. Above all, it is known to use commercial polymerization processes in suspension, bulk, emulsion and also in solution for EVAC with VAC contents of about 45% (EVAC-45 obtained by medium-pressure polymerization), vinyl chloride (VC) in particular being used for the production of PVC modifiers. graft polymerized in varying amounts (DE 1495694, DE 1544859, DE 1495737, DE 1544873, DE 1495813, DE 1261673, US 3517083, FR 1456458, US 3322858, GB 1126316, GB 1020704, FR 1511927, DE 1745289, DE 1770119). In this case, the polymerization batch except VC as a main monomer also contain other comonomers (GB 1097019, DE 1495735), the EVAC used pre-crosslinked (DE 1544859, DE 1770107) or the VAC groups have been previously partially saponified (DE 1495737, DE 1261673). In addition to various esters, the comonomers added to the VC include acrylic acid (AS) and methacrylic acid (MSA) under the conditions of customary industrial polymerization processes (BeIg. 702904). When low cost EVAC high pressure polymers with VAC contents between 5 and 25% (EVAC-5/25) are used, the gel phase polymerisation, i.e., graft modification technology, has been used. H. the "coupling" of grafts on the swollen by the monomer backbone chains, as an advantageous polymerization process for a number of important vinyl monomers, especially VC, vinyl acetate, styrene, (meth) acrylic acid esters and optionally their mixtures with each other, proved. (DD 122686, DD 134232, DD 158908, DD 245670 A1, DD 211571, DD 131752, DE 2421900; Tachibano, M .; Plastics Ind. News [1981] Nov., pp. 167-171; Gerecke, J., u. al .; Plastic and Kautschuk27 [1980] 8, S.422-424; ibid 32 [1985] 9, p. 332/333).