Use of vinyl acetate-copolymers as a shrinkage-reducing additive in cold-curing systems

Abstract

The invention relates to the use of vinyl acetate-copolymers as a shrinkage-reducing additive (low profile additive) in cold-curing systems for producing composite materials, characterized in that vinyl acetate-copolyerisate of 40 to 95 wt % vinyl acetate and 5 to 60 wt % of one or more co-monomers from the group containing vinyl esters of unbranched or branched carboxylic acids having 3 to 20 C-atoms and methacrylic acid esters and acrylic acid esters of unbranched or branched alcohols having 2 to 15 C-atoms are used, wherein the specifications in wt % relate to the total weight of the co-monomers and add up to 100 wt %.

Claims

1. A method for producing a cold-curing unsaturated polymer system for producing composite materials, which cures at a temperature less than 60° C., comprising: mixing constituents comprising: a) at least one crosslinkable, unsaturated polyester resin or vinyl ester resin, b) at least one ethylenically unsaturated monomer, c) at least one peroxide and/or hydroperoxide, d) at least one cobalt salt accelerator, e) optionally fiber material, and f) optionally mineral fillers; and g) a shrinkage-reducing admixture, the shrinkage reducing admixture comprising a vinyl acetate copolymer of 40 to 95 wt % of vinyl acetate and 5 to 60 wt % of one or more vinyl-functional comonomers selected from the group consisting of vinyl esters of unbranched or branched carboxylic acids having 3 to 20 carbon atoms, (meth)acrylic esters of unbranched or branched alcohols having 2 to 15 carbon atoms, and mixtures thereof wherein the percentages in wt % are based on the total weight of comonomers in the vinyl acetate copolymer.

2. The method of claim 1, wherein the vinyl acetate copolymers comprise 55 to 95 wt % vinyl acetate and 5 to 45 wt % of vinyl-functional comonomers, based on the total weight of all monomers.

3. The method of claim 1, wherein the shrinkage reducing admixture comprises at least one vinyl acetate copolymer of vinyl acetate with comonomers selected from the group consisting of vinyl laurate and vinyl esters of α-branched monocarboxylic acids having 9 to 10 carbon atoms, and mixtures thereof.

4. The method of claim 1, wherein the shrinkage reducing admixture comprises at least one vinyl acetate copolymer of vinyl acetate with one or more comonomers selected from the group consisting of ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-, iso- and tert-butyl acrylate, n-, iso- and tert-butyl methacrylate, 2-ethylhexyl acrylate, norbornyl acrylate, and mixtures thereof.

5. The method of claim 1, wherein the vinyl acetate copolymer consists of a copolymer of 40 to 95 wt % of vinyl acetate and 5 to 60 wt % of one or more vinyl-functional comonomers selected from the group consisting of vinyl esters of unbranched or branched carboxylic acids having 3 to 20 carbon atoms, (meth)acrylic esters of unbranched or branched alcohols having 2 to 15 carbon atoms and mixtures thereof, wherein the percentages in wt % are based on the total weight of comonomers in the vinyl acetate copolymer, with no further comonomers.

6. The method of claim 1, wherein the vinyl acetate copolymer is prepared by bulk polymerization or solution polymerization.

7. The method of claim 1, wherein the shrinkage-reducing admixture is free of polyvinyl alcohol protective colloid.

8. The method of claim 1, wherein the cold curing system cures at a temperature of 40° C. or less.

9. The method of claim 1, wherein the cold-curing system comprises a polymer concrete which is cement-free.

10. The method of claim 1, wherein styrene is present as an ethylenically unsaturated monomer.

11. The method of claim 1, wherein the composition cures at a temperature of from 0° C. to 40° C.

12. A cold-curing, radically crosslinkable unsaturated polymer composition for producing composite materials which cures at a temperature of less than 60° C., comprising: a) at least one crosslinkable, unsaturated polyester resin or vinyl ester resin, b) at least one ethylenically unsaturated monomer, c) at least one peroxide and/or hydroperoxide initiator, d) at least one cobalt salt accelerator, e) optionally fiber materials, f) optionally mineral fillers, and g) a polyvinyl acetate copolymer comprising 40 to 95 wt % vinyl acetate and 5 to 60 wt % of one or more vinyl-functional comonomers selected from the group consisting of vinyl esters of unbranched and branched carboxylic acids having 3 to 20 carbon atoms and methacrylic esters and acrylic esters of unbranched or branched alcohols having 2 to 15 carbon atoms, the figures in wt % being based on the total weight of all comonomers and adding up to 100 wt %.

13. The crosslinkable polymer composition of claim 12, which cures at a temperature in the range of 0° C. to 40° C.

14. The cold-curing, radically crosslinkable polymer composition of claim 12, wherein the mineral filler f) comprises at least one mineral filler selected from the group consisting of quartz, basalt, granite, chalk, expanded clay, perlite, and cement, wherein cement, if present, does not act as a binder.

15. The composition of claim 12, which cures to a polymer concrete.

16. The composition of claim 15, which is free of cement.

17. The composition of claim 12, wherein styrene is present as an ethylenically unsaturated monomer.

18. The composition of claim 12, wherein the shrinkage-reducing admixture contains no polyvinyl alcohol protective colloid.

19. The composition of claim 12, wherein the polyvinyl acetate copolymer has been prepared by bulk or solution polymerization.

20. The composition of claim 12, wherein the polyvinyl acetate copolymer is a copolymer of vinyl acetate with a copolymer selected from the group consisting of vinyl laurate, vinyl esters of α-branched C.sub.9-C.sub.10 monocarboxylic acids, and mixtures thereof.

21. The composition of claim 12, wherein the shrinkage-reducing additive consists of 40 to 95 wt % of vinyl acetate and 5 to 60 wt % of one or more vinyl-functional comonomers selected from the group consisting of vinyl esters of unbranched or branched carboxylic acids having 3 to 20 carbon atoms, (meth)acrylic esters of unbranched or branched alcohols having 2 to 15 carbon atoms, and mixtures thereof wherein the percentages in wt % are based on the total weight of comonomers in the vinyl acetate copolymer, optionally in dissolved form.

Description

Example 1

Preparation of a Vinyl Acetate Copolymer 1

(1) A 2 l stirred glass vessel with anchor stirrer, reflux condenser and metering facilities was charged with 40.0 g of vinyl acetate, 21.2 g of vinyl laurate, 22.1 g of isopropanol and 0.5 g of PPV (tert-butyl perpivalate, 75% solution in aliphatics). The initial charge was subsequently heated to 70° C. under nitrogen at a stirrer speed of 200 rpm. When the internal temperature reached 70° C., 200.0 g of vinyl acetate, 81.7 g of vinyl laurate, 6.2 g of isopropanol and initiator solution (0.8 g of PPV) were metered in. The monomer solution was metered in over the course of 240 minutes, and the initiator solution over the course of 300 minutes. After the end of the initiator feeds, polymerization was continued at 80° C. for 3 hours. Under reduced pressure and at elevated temperature, volatile constituents were removed by distillation. The Höppler viscosity of the copolymer, determined according to DIN 53015 (10% in ethyl acetate at 20° C.), was 2.4 mPas, its number-average molecular weight M.sub.n was 15 000 g/mol, its weight-average molecular weight M.sub.w was 55 400 g/mol, determined by size exclusion chromatography in THF at 60° C. relative to narrow-range polystyrene standards.

Example 2

Preparation of a Vinyl Acetate Copolymer 2

(2) A 2 l stirred glass vessel with anchor stirrer, reflux condenser and metering facilities was charged with 40.0 g of vinyl acetate 21.2 g of VeoVa® 10, 22.1 g of isopropanol and 0.5 g of PPV (tert-butyl perpivalate, 75% solution in aliphatics). The initial charge was subsequently heated to 70° C. under nitrogen at a stirrer speed of 200 rpm. When the internal temperature reached 70° C., 200.0 g of vinyl acetate, 81.7 g of VeoVa® 10, 6.2 g of isopropanol and initiator solution (0.8 g of PPV) were metered in. The monomer solution was metered in over the course of 240 minutes, and the initiator solution over the course of 300 minutes. After the end of the initiator feeds, polymerization was continued at 80° C. for 3 hours. Under reduced pressure and at elevated temperature, volatile constituents were removed by distillation.

(3) The Höppler viscosity of the copolymer, determined according to DIN 53015 (10% in ethyl acetate at 20° C.), was 2.5 mPas, its number-average molecular weight M.sub.n was 14 000 g/mol, its weight-average molecular weight M.sub.w was 53 400 g/mol, determined by size exclusion chromatography in THF at 60° C. relative to narrow-range polystyrene standards.

Example 3

Preparation of a Vinyl Acetate Copolymer 3

(4) A stirred tank was charged with 2 kg of isopropanol together with 33.6 kg of vinyl acetate, 8.4 kg of vinyl laurate and 10 g of tert-butyl peroxo-2-ethylhexanoate, and the polymerization was commenced by heating to 72° C. At the start, a further 7 g of butyl peroxo-2-ethylhexanoate were added, and then 170 g of butyl peroxo-2-ethylhexanoate in 700 q of isopropanol were metered in over 6 hours. 240 minutes after the start, the metering of 28 kg of vinyl acetate was commenced, and this metering was continued over a period of 120 minutes. After the end of the metering of vinyl acetate, stirring was continued for 60 minutes more, the temperature was raised to 120° C., the tank was evacuated, and solvent and residual monomer were removed by distillation.

(5) The Höppler viscosity of the copolymer, determined according to DIN 53015 (10% in ethyl acetate at 20° C.), was 5.5 mPas, its number-average molecular weight M.sub.n was 14 000 g/mol, its weight-average molecular weight M.sub.w was 137 000 g/mol, determined by size exclusion chromatography in THF at 60° C. relative to narrow-range polystyrene standards.

(6) Testing of the use of the vinyl acetate copolymers as shrinkage-reducing admixtures (LPAs):

(7) 1.) Curing of UP resin compositions at 23° C.:

(8) A mixture was produced from the raw materials listed in Table 1, and was briefly degassed. The density D.sub.p of the degassed mixture was ascertained, and the mixture was then poured into a mold and cured at room temperature (23° C.) for 48 hours. Finally, the density D.sub.c of the cured molding was determined. The shrinkage was ascertained by comparing the density D.sub.p of the mixture prior to curing with the density D.sub.c of the molding after curing, using the formula Shrinkage (%)=(D.sub.c−D.sub.p/D.sub.c)×100 (Table 2). Minus values indicate that the molding after curing was larger than the original mold.

(9) The density was measured in each case using the DMA 38 density measuring apparatus (manufacturer: Anton Paar GmbH) at room temperature (23° C.).

(10) TABLE-US-00001 TABLE 1 Formulation for polymeric moldings: Parts by Type Raw material weight Palapreg ® P18-03 UP resin (around 65.0% in styrene) 80.0 LPA LPA (40% in styrene) 20.0 Butanox ® M 50 Peroxide 1.5 Akzo Nobel NL-49 Accelerator (1% Co in ester) 0.5

(11) Low profile additives (LPAs) used were as follows:

(12) LPAC1 (comparative):

(13) Vinnapas® C501 (acid-modified polyvinyl acetate from Wacker Chemie AG).

(14) LPAC2 (comparative):

(15) Vinnapas® B 100 SP (polyvinyl acetate from Wacker Chemie AG).

(16) LPAC3 (comparative):

(17) Degalan LP 53/13 (acid-modified polymethyl methacrylate from Evonik AG).

(18) LPAC4 (comparative):

(19) Modiper® SV10 A (acid-modified styrene/vinyl acetate block copolymer from Nippon Oil and Fats Company, Limited).

(20) LPA1:

(21) Vinyl acetate copolymer 1 with 70 wt % vinyl acetate and 30 wt % vinyl laurate

(22) LPA2:

(23) Vinyl acetate copolymer 2 with 70 wt % vinyl acetate, 24 wt % VeoVa®10 and 6 wt % vinyl laurate

(24) LPA3:

(25) Vinyl acetate copolymer 3 with 88 wt % vinyl acetate and 12 wt % vinyl laurate

(26) TABLE-US-00002 TABLE 2 Shrinkage of the moldings: Density D.sub.p of the Density D.sub.c of the mixture prior to molding after curing curing at 23° C. Shrinkage LPA [g/mm.sup.3] [g/mm.sup.3] [%] — 1.093 1.195 8.53 LPA1 1.055 1.047 −0.76 LPA2 1.059 1.077 1.67 LPA3 1.052 1.063 1.03 LPAC1 1.062 1.150 7.65 LPAC2 1.064 1.162 8.43 LPAC3 1.063 1.149 7.48 LPAC4 1.041 1.112 6.38

(27) From Table 2 it is evident that conventional LPAs (LPAC1-LPAC4) have virtually no activity, or none, at room temperature (here 23° C.). Relative to the formulations of the invention with vinyl acetate copolymers (LPA1, LPA2 and LPA3), the comparative substances LPAC1 to LPAC4 showed virtually no activity in the room-temperature curing.

(28) The hydrophobic vinyl acetate copolymers LPA1, LPA2 and LPA3, in contrast, exhibited very good activity even at 23° C., hence resulting in a significantly reduced shrinkage and even, in the case of LPA1, in slight expansion.

(29) 2.) Curing of polymer concrete compositions at 23° C.:

(30) A polymer concrete mixture was produced from the raw materials listed in Table 3, and the mixture was poured into a mold and cured at room temperature (23° C.) for 48 hours. For this purpose, the mixture was introduced into a silicone mold having internal dimensions of 10 mm×50 mm×1000 mm, whose base was lined with a perforated metal sheet (1000 mm×50 mm×1 mm) as a backing. If the polymer concrete composition shrinks during the cure, the specimen bulges upward, with the curvature increasing in line with the shrinkage. The height of the curvature in the center of the specimen relative to the ends of the specimen was measured in mm. The linear shrinkage was calculated from this, using the following formula:
Thickness(mm)×curvature(mm)/125(mm×m)=mm/m.
A linear shrinkage of 1 mm/m then corresponds to 0.1%.

(31) Tables 3 and 4:

(32) Formulation and testing for polymer concrete moldings:

(33) TABLE-US-00003 TABLE 3 Test Run (TR), constituents in parts by weight TR1 TR2 TR3 TR4 Quartz sand 8a - HR 0.1 - 0.6 T 26.7 26.7 26.7 26.7 Quartz sand 4extra - HR 1 - 1.8 T 26.7 26.7 26.7 26.7 Quartz sand F 36 26.7 26.7 26.7 26.7 Palatal P61/02 UP resin from 20 17 14 13 Aliancys AG Accelerator NL-49P Co accelerator 0.5 0.1 0.1 0.1 from AkzoNobel Curox M-312 epoxide curative, 1 1 1 1 United Initiators LPA3 solution (40% in styrene) 0 3 6 7 Linear shrinkage % 0.43 0.20 0.08 0.03

(34) TABLE-US-00004 TABLE 4 Test Run (TR), constituents in parts by weight TR5 TR6 TR7 Quartz sand 8a - HR 0.1 - 0.6 T 17.5 17.5 27.5 Quartz sand 4extra - HR 1 - 1.8 T 0 0 0 Quartz sand F 36 17.5 17.5 17.5 Palatal P61/02 UP resin from 25 16.25 16.25 Aliancys AG Accelerator NL-49P Co accelerator 0.1 0.07 0.07 from AkzoNobel Curox M-312 epoxide curative, 1 1 1 United Initiators LPA3 solution (40% in styrene) 0 8.75 8.75 Omyacarb - 40GU chalk from Omya 40 40 30 Linear shrinkage % 0.63 0.01 0.02

(35) Discussion of Results:

(36) A feature of the vinyl acetate-vinyl laurate copolymer used in the formulation of polymer concrete moldings is that the viscosity in a 40 wt % styrene solution is only around 1000 mPas (Brookfield viscosity at 23° C., 100 rpm, spindle 4). Such low viscosities are essential for effective wetting of fibers and fillers, and are a prerequisite for formulations with high fractions of solid and/or fiber. The redispersible vinyl acetate-vinyl versatate copolymers mentioned in EP 337931 B1 as a shrinkage-reducing admixture, in contrast, even at a concentration of 20 wt % in styrene, lead to a viscosity of 100 000 mPas or more (Brookfield viscosity at 23° C., 100 rpm, spindle 4).

(37) Even in a very small fraction, the vinyl acetate copolymers act very effectively as shrinkage-reducing admixtures in polymer concrete formulations. The Test Run TR3 shows that even at a low fraction of 6 wt %, a substantial reduction in shrinkage is obtained (wt % based on the total weight of resin a) and monomer b) and vinyl acetate copolymer).