JPS61296058A - Thermosetting resin composition - Google Patents

Abstract

PURPOSE:To produce a composition having remarkably improved cure shrinkage and giving a molded article having excellent surface smoothness, by compounding an unsaturated polyester, a specific ethylene-acrylic acid ester copolymer and styrene. CONSTITUTION:(A) 20-55pts.(wt.) of an unsaturated polyester having a molecular weight of 2,000-5,000 (preferably 150-200 per double bond) is compounded with (B) 5-30pts. of an ethylene-acrylic acid ester copolymer having an ethylene content of 10-50wt%, preferably 15-30wt% and (C) 40-65pts. of styrene.

Description

Detailed Description of the Invention (Industrial Field of Application) - The present invention relates to a polyester resin composition, more specifically a polyester resin composition containing an ethylene-acrylic ester copolymer having an ethylene content of 10 to 50% by weight. The present invention relates to a thermosetting resin composition that has improved curing shrinkage and provides molded products with good surface smoothness.

(Prior art and its problems) Unsaturated polyester resin is used for various purposes due to its low cost and low viscosity, but when it polymerizes and hardens, it inevitably undergoes volumetric shrinkage, causing ribs, bosses, etc. in molded products. It has the disadvantage of causing sink marks, warping, and even cranking on the back.

In order to improve this point, sheet molding compounds (abbreviated as SMC) and bulk molding compounds (BMC) made of unsaturated polyester resin have been developed.
Thermoplastic polymers such as polystyrene and polymethyl methacrylate are added to suppress shrinkage. In recent years, SMC and BMC have begun to be used for the outer panels of automobiles, and there is a demand for materials with good surface smoothness and paintability. Vinyl acetate polymer, styrene-butadiene block polymer, and saturated polyester resin have been newly developed as low-shrinkage agents, but even with the use of these, long waves, Distortion (situ wave) and dimple-like dents occur in short sections, and it is still not satisfactory.

(Means for Solving the Problems) As a result of studying various methods for reducing shrinkage, the present inventors found that an ethylene-acrylic acid ester copolymer with a relatively low ethylene content has excellent surface smoothness with few of the above-mentioned drawbacks. The inventors have discovered that a molded product can be obtained, and have completed the present invention.

That is, 20 to 55 parts (by weight, the same applies hereinafter) of unsaturated polyester, 5 to 30 parts of ethylene-acrylic acid ester copolymer with an ethylene content of 10 to 50% by weight, and 40 to 40 parts of styrene.
It is an object of the present invention to provide a thermosetting resin composition comprising 65 parts.

The unsaturated polyester used in the present invention is a polyester obtained by containing as essential components an unsaturated carboxylic acid having a valence of 2 or more or its anhydride and an alcohol having a valence of 2 or more.

Such unsaturated polyesters include unsaturated dibasic acids such as maleic acid, maleic anhydride, and fumaric acid, and saturated polyesters such as phthalic acid, phthalic anhydride, isophthalic acid, tetrahydrophthalic anhydride, succinic acid, and adipic acid, which can optionally be used in combination. Those obtained by the reaction of dibasic acids with alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3- or 1,4-butylene glycol, neopentyl glycol, hydrogenated bisphenol A1 glycerin, etc. It is.

The molecular weight of such polyester is usually 2000 to 500.
0, and the molecular weight per double bond is 150~
A value of 200 is preferable, and a value as close to 150 as possible is more preferable because the surface smoothness is better. The amount used is 20 to 55 parts in the composition, preferably 30 to 45 parts. If the amount is less than 20 parts, the mechanical strength will be poor, and
If it exceeds 0 parts, the viscosity of the composition will be high and the impregnating properties of glass fibers during the production of SMC and BMC will be poor.

The ethylene-acrylic acid ester copolymer used in the present invention has an ethylene content of 10 to 50% by weight, preferably 15 to 30% by weight. If the ethylene content in the copolymer deviates from the above range, the curing shrinkage of the composition will not be sufficiently improved, and the composition will have poor surface smoothness and impact strength, which is undesirable. The above ethylene
Examples of the acrylic ester copolymer include Bemac, a trade name manufactured by DuPont. In addition, the amount thereof is 5 to 30 parts in the composition, preferably 10 to 25 parts. If the amount is less than 5 parts, the low shrinkage effect will be poor;
If it exceeds 0 parts, the mechanical strength, especially the elastic modulus, decreases. In addition to these, other low-shrinkage agents such as saturated polyester, polyvinyl acetate, polystyrene, acrylic polymer, etc. can also be used in combination.

Also, in the composition of the present invention, 40 to 65 parts by weight of styrene is used. In addition to such styrene, α-methylstyrene, vinyltoluene, divinylbenzene, acrylic ester, methacrylic ester, etc. can also be used in combination.

In addition to the curing catalyst, a curing accelerator, a polymerization inhibitor, a filler, a reinforcing material, a thickener, an internal mold release agent, a pigment, etc. can be added to the composition of the present invention depending on the purpose.

As a curing catalyst, benzoyl peroxide, t-butyl perbenzoate, t-butyl peroctoate,
These are organic peroxides such as dicumyl peroxide, di-t-butyl peroxide, and trimethylcyclohexanone perketal.

Examples of the polymerization inhibitor include hydroquinone, parabenzoquinone, catechol, and toluhydroquinone, and examples of the curing accelerator include cobalt naphthenate, cobalt octoate, cobalt acetylacetate, and dimethylaniline.

Filling materials include calcium carbonate, clay, hydrated alumina, quartz sand, glass flakes, glass bubbles, mica powder, etc., and reinforcing materials include roving or chopped strands obtained from it and glass fibers in the mat form thereof. , carbon fiber, metal fiber, organic fiber, etc. In particular, the appropriate amount of reinforcing material to be used is 20 to 35% by weight of the composition including the reinforcing material.

Internal mold release agents include fatty acid metal salts such as zinc stearate and waxes such as polyalkylene ethers. Further, as the thickener, alkaline earth metals such as magnesium oxide, calcium oxide, magnesium hydroxide, and calcium hydroxide, and isocyanate compounds are used.

(Effects of the Invention) When the composition of the present invention is applied to SMC and BMC, it provides a molded product with excellent surface smoothness and also has the effect of significantly suppressing the occurrence of cracks due to impact. , compression molding, injection molding, and transfer molding, such as automobile hoods, roofs, tailgates, rear spoilers, doors, bumper covers, lamp housings, trunk lids, fenders, undercarriages, and furniture such as chairs and tables. It can be used for casings, housings, etc. of electrical parts.

(Example) The present invention will be further explained with reference to Examples and Comparative Examples. Note that parts and percentages in the examples are based on weight.

Synthesis Example 1 Synthesis of unsaturated polyester resin (a) 912 g of propylene glycol and 1160 g of fumaric acid were reacted at 200° C. for 16 hours in a nitrogen gas stream to obtain a polyester with an acid value of 38. This is unsaturated polyester (A)
shall be. Next, 0.1g of hydroquinone and 72g of styrene
0 g was added and dissolved to obtain a liquid resin with a nonvolatile content of 70%. This is called resin A.

(b) 780 g of neopentyl glycol and 415 g of isophthalic acid were reacted at 210° C. in a nitrogen gas stream for 8 hours to obtain an acid value of 7. Then propylene glycol 627
g and 1450 g of fumaric acid were added thereto and reacted at 200° C. for 12 hours to obtain a polyester with an acid value of 33. This is referred to as unsaturated polyester (B). Next, 0.3 g of hydroquinone and 1380 g of styrene were added and dissolved to obtain a liquid-6 resin with a non-volatile content of 70%. This will be referred to as resin B.

Synthesis Example 2 <Synthesis of ethylene-acrylic acid ester copolymer> Methylene chloride 200m7! Methyl acrylate 1
A solution of 7.2 g (0.20 g mol) and 0.15 g of 2,2'-azobis[2-methylpropionitrile] was saturated with 13.5 g (0.20 g mol) of boron trifluoride. , and placed in a 400 mJ volume shaker tube. After cooling and degassing in a crushed solid carbon dioxide bath, the tube was pressurized with 75 g (2,000 grams moles) of ethylene. Next, the liquid tube was shaken at 25° C. for 12 hours to complete the copolymerization. The gas was removed and the product was removed from the shaker tube and the resulting mixture was then passed through steam to remove volatiles including boron trifluoride and solvent.

The separated polymer was dissolved in acetone, the resulting solution was filtered, then precipitated from the filtrate by the addition of steam, washed twice with a 50:50 methanol-water solution in a blender mixer, and vacuum Dry in an oven at 80°C. Ethylene-methyl acrylate copolymer is 22.
1 g was obtained.

The resulting copolymer was subjected to elemental analysis of carbon and hydrogen, and the oxygen content was calculated to determine the amount of methyl acrylate component, which was 78% and the ethylene content was 22%.

Examples 1 to 3, Comparative Examples 1 to 5 50 parts of the resin (A) synthesized in Synthesis Example 1, 40% of the ethylene-methyl acrylate copolymer synthesized in Synthesis Example 2,
50 parts of 30% or 20% styrene solution, 1 part of t-butyl perbenzoate, 3 parts of zinc stearate, and 180 parts of calcium carbonate were mixed. After adding 1.5 parts of magnesium oxide to these, each SMC was manufactured by mixing these with 1 inch long glass fiber so that the glass content was 30%.

For comparison, instead of the styrene solution of the ethylene-methyl acrylate copolymer, Vylon 560 (manufactured by Toyobo) as a saturated polyester, Dick Styrene CR-3500 (manufactured by Dainippon Ink & Chemicals) as polystyrene, Each SMC was prepared using 50 parts of a 30% styrene solution of Acryvet NDK (manufactured by Mitsubishi Rayon ■) as polymethyl methacrylate and LP-60 (manufactured by Union Carbide ■) as polyvinyl acetate.

Next, each of the above SMCs was aged at 60°C for 24 hours, and then aged for 3
Pour 100 kg into a mold of 00 Tsuru x 500 Tsuru at 140℃.
A flat plate with a thickness of 3 cranes was prepared using a pressure of /-, and the smoothness of the surface of the molded product was evaluated. In addition, cure shrinkage rate and bending strength are determined according to JIS
Determined by K-6911, 15 for falling ball impact resistance
A 500 g steel ball was dropped from a height of 100 cm on a QmmX 15 QmX 3n+ test piece using a falling ball impact tester (Toyo Seiki Seisakusho), and the crank produced on the back of the test piece was determined. These results are shown in Table 1.

The composition of the present invention has a very small curing shrinkage rate and rather expands, so the surface smoothness of the molded product is excellent. Further, it is possible to provide a flexible and flexible molded product with a small bending modulus and excellent ball impact resistance. On the other hand, all of the compositions using other low-shrinkage agents in Comparative Examples had poor surface smoothness, and cracks were significantly generated due to impact from falling balls.

The physical property evaluations in Table 1 are as follows.

- Falling ball impact resistance: After the falling ball test, apply flaw detection agent to the back of the test piece and check the condition of the crank.

0-11~Almost no cracks △---- Some cranks ×-111 Cracks on the entire surface ・Surface smoothness: Comprehensive condition of warpage, long waves, short waves, and dimple-like dents on the test piece Judgment is made.

○----Very good △----Slightly good ×--Positive Example 4 42.9 parts of the resin (B) synthesized in Synthesis Example 1 and Synthesis Example 2
3 of the ethylene-methyl acrylate copolymer synthesized in
SMC was produced in the same manner as in Example 1 using 50 parts of 0% styrene solution, and the cured product was evaluated. The results are shown in Table 2.

Table 2

Claims (1)

[Claims] 20-55 parts by weight of unsaturated polyester, ethylene content 1
A thermosetting resin composition comprising 5 to 30 parts by weight of 0 to 50% by weight of ethylene-acrylic acid ester copolymer and 40 to 65 parts by weight of styrene.