JPH07150024A - Shrinkage-reducing composition for unsaturated polyester resin - Google Patents

Abstract

PURPOSE:To obtain a shrinkage-reducing composition which has good sheet releasability after the viscosity is increased, causing no staining on the mold surface, holds low shrinkage and high mechanical strength and has good appearance by using a styrene polymer prepared by making the polymerization of a specific monomer composition terminated at a specific polymerization rate. CONSTITUTION:A monomer composition comprising (A) 100 pts.wt. of a mixture of (i) 90 to 99.9wt.% of styrene and (ii) 10 to 0.1wt.% of a polymerizable monomer bearing carboxyl groups and (B) 0.01 to 1 pts.wt. of a chain transfer agent is subjected to bulk polymerization until the polymerization rate reaches 10 to 70% to give objective composition of 0.1 to 50mg/KOH/g acid value. It is preferred that, for example, acrylic or methacrylic acid is used as component ii; n-dodecylmercaptan, as component B, and hydroquinone, as a polymerization terminator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shrinkage-reducing agent composition for unsaturated polyester resins, and more specifically, it has improved compatibility with unsaturated polyester resins and workability at the time of thickening, and has a good appearance. The present invention relates to a styrene-based polymer low-shrinking agent composition from which a molded product is obtained.

[0002]

BACKGROUND OF THE INVENTION Unsaturated polyester resins are used in a wide range of fields as raw materials for fiber reinforced plastics (FRP). Since the shrinkage rate of the unsaturated polyester resin itself is 5-12% when it is cured,
The molded product is warped, glossy, wavy, cracked and the like. On the other hand, as a means for reducing the shrinkage ratio, it is common to blend a thermoplastic resin such as polyvinyl acetate, polymethyl methacrylate, polyethylene or polystyrene into an unsaturated polyester resin. Is said to be a low-contracting agent.

When blended with an unsaturated polyester resin, depending on whether the two are completely melted or dispersed in the unsaturated polyester resin in a droplet state, the shrinkage reducing agent is a compatible system (homogeneous system). ) And an incompatible system (dispersion system). Among them, polyvinyl acetate, polymethyl methacrylate and the like are compatible and have a low shrinkage effect, but have a drawback that the molded product has low mechanical strength.

On the other hand, conventionally used polyethylene, polystyrene and the like are incompatible ones, and the obtained molded product has excellent characteristics such as good coloring property and pigment dispersibility and high mechanical strength. However, for example, when a sheet molding compound (SMC) is prepared by blending an unsaturated polyester resin with polystyrene as a shrinkage reducing agent and magnesium oxide (MgO) as a thickening agent, this polystyrene is Since it does not mix with the saturated polyester resin, the following two problems occur. That is, when forming a metal bridge between the carboxyl group of the unsaturated polyester resin and magnesium oxide, in the so-called thickening step, the unsaturated polyester resin and polystyrene undergo phase separation, when peeling the sheet after thickening Stringing and stickiness occur. The polystyrene in the unsaturated polyester resin separates and floats up on the surface of the molded product, remarkably impairing its appearance, and the separated polystyrene contaminates the mold surface and hinders mold release, so-called scumming.
ng) cause a phenomenon.

In order to prevent these problems, it has been attempted to use a styrene-based polymer having a carboxyl group introduced therein as a shrinking agent (Eiichiro Takiyama, Polyester Resin Handbook, pages 633-636, Nikkan Kogyo Shimbun (1988)). Described in). This intends to form a metal oxide bond between the carboxyl group of this polymer and that of the unsaturated polyester resin. However, the obtained polymer is a mixture from a styrene copolymer containing a large amount of carboxyl groups to a polystyrene not containing it, and since the number of effective copolymers therein is very small, its effect is Not enough.

The present invention maintains the excellent characteristics of the conventional incompatible low-contracting agents, that is, the molded product has good coloring property and pigment dispersibility and high mechanical strength, and at the same time, has a high viscosity. It is an object of the present invention to improve the peelability of the sheet afterwards and to obtain a molded product having a good appearance without causing a scumming phenomenon.

[0007]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, the amount ratio of styrene and a monomer having a carboxyl group was identified as a low-shrinking agent. The present inventors have found the fact that it is effective to use a styrene-based polymer obtained by terminating a different monomer composition at a specific polymerization rate, and arrived at the present invention. It is considered that the reason why the polymer obtained under such conditions exhibits a sufficient effect is that the copolymer containing a carboxyl group in the polymer is uniform with little variation.

That is, the present invention relates to styrene 90-99.9.
Polymerizable monomer having weight% and carboxyl group 10 to 0.
With respect to 100 parts by weight of the monomer composition consisting of 1% by weight,
Add 0.01 to 1 part by weight of a chain transfer agent to perform bulk polymerization to obtain a polymerization rate.
It is obtained by stopping the polymerization at 10-70% and has an acid value of 0.1-50 mg-
A low-shrinking agent composition for unsaturated polyester resins, characterized by having KOH / g.

In the present invention, the polymerizable monomer having a carboxyl group has a carboxyl group and a radically polymerizable double bond such as acrylic acid, methacrylic acid, maleic acid and itaconic acid. Any of the above can be used. Further, the polymerizable monomer having a carboxyl group is preferably in the range of 0.1 to 10% by weight in the monomer composition containing styrene. If this amount is less than 0.1% by weight, the resulting polymer has few carboxyl groups, the low-shrinking agent separates during thickening, and
The mold surface is contaminated and the appearance of the molded product is not good. If it exceeds 10% by weight, the polymer is precipitated during the polymerization, so that it is not suitable as a shrinkage reducing agent.

The bulk polymerization of styrene in the present invention is carried out at atmospheric pressure or under pressure in a reaction vessel in an atmosphere of an inert gas such as nitrogen,
Thermal radicals generated by heating a monomer composition composed of styrene and a polymerizable monomer having a carboxyl group, and / or 2,2′-azobisisobutyronitrile (hereinafter referred to as AIB).
Abbreviated as N. ), A known radical polymerization initiator such as benzoyl peroxide, etc. is added to the monomer composition,
It is initiated by radicals generated from the polymerization initiator. At this time, the polymerization temperature is usually 50 to 220 ° C, preferably 8
It is 0 to 150 ° C.

In the above bulk polymerization, the molecular weight of the styrene polymer obtained is adjusted to 5,000 to 500,000 by adding a chain transfer agent. The chain transfer agent may be any one as long as it is usually used for polymerization or copolymerization of radically polymerizable monomers. For example, mercaptans such as methyl mercaptan, t-butyl mercaptan, decyl mercaptan, benzyl mercaptan, lauryl mercaptan, stearyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, mercaptoacetic acid, mercaptopropionic acid; methanol, propanol, butanol, isopropanol. Butanol,
t-butanol, hexanol, benzyl alcohol,
Alcohols such as allyl alcohol; halogenated hydrocarbons such as chloroethane, fluoroethane, trichloroethylene, carbon tetrachloride and the like can be mentioned. Among them, the ease of adjusting the molecular weight, and further, when the obtained styrene polymer and the unsaturated polyester resin are mixed and cured,
Mercaptans are preferable, and n-dodecyl mercaptan (hereinafter abbreviated as n-DM) is more preferable, from the viewpoint of improving the compatibility of both and not hindering the curing.

The amount of the chain transfer agent in the present invention is usually 0.01 to 1 part by weight, preferably 0.05 to 0.5 part by weight, based on 100 parts by weight of styrene. If this amount is less than 0.01 parts by weight, the viscosity of the polymerization system becomes high, which makes it difficult to manufacture, and the workability at the time of impregnating the mixture of the obtained composition and the unsaturated polyester resin into the reinforcing material decreases. To do. Further, the surface of the molding die is contaminated and the appearance of the molded product is not good. On the other hand, if this amount exceeds 1 part by weight, the molecular weight of the styrene-based polymer obtained will decrease, and the mechanical strength of the molded product will significantly decrease. This chain transfer agent may be charged all at once in the reaction vessel before the polymerization, or may be added continuously or sequentially during the polymerization.

In the present invention, the polymerization rate of styrene is 1
When it reaches 0-70%, the polymerization is stopped. If the polymerization rate is less than 10%, the amount of the styrene-based polymer, which is effective in reducing the shrinkage of the molded product, will be small, and if it exceeds 70%, the viscosity of the polymerization system will be high, which is not preferable. By the way, by stopping the polymerization, a large amount of unreacted styrene remains in the produced styrene-based polymer, but this is not inconvenience at all, and work at the time of blending this composition and the unsaturated polyester resin. It is more convenient because it improves the quality.

Any known method may be used as a method for terminating the above polymerization as long as the chain transfer of the growing radicals is stopped and disappears. To do this, add 50 to 5,
The operation may be performed by adding 000 ppm of a polymerization terminator, blowing oxygen or air into the polymerization solution, cooling the polymerization solution to 40 ° C. or less, and these may be used alone or in combination.

The term "polymerization terminator" as used herein means that it rapidly reacts with radicals generated from styrene and / or a polymerization initiator,
It is a drug that converts into a stable radical or neutral substance that does not subsequently cause polymerization. Specific examples thereof include quinones such as p-benzoquinone, naphthoquinone, phenanthraquinone, and 2,5-diphenyl-p-benzoquinone; hydroquinone, pt-butylcatechol, and 2,5-di-t-butylhydroquinone. , Hydroquinones such as mono-t-butylhydroquinone and 2,5-di-t-butylhydroquinone; phenols such as di-t-butyl para-cresol hydroquinone monomethyl ether and α-naphthol;
Organic / inorganic copper salts such as copper naphthenate; Amidines such as acetamidine acetate and acetamidine sulfate;
Hydrazine salts such as phenylhydrazine hydrochloride and hydrazine hydrochloride; quaternary ammonium salts such as trimethylbenzylammonium chloride, laurylpyridinium chloride, cetyltrimethylammonium chloride and phenyltrimethylammonium chloride; polyhydric phenols such as pyrogallol, tannic acid and resorcinol Kinds; nitro compounds and oximes can be mentioned.

The styrene-based polymer composition obtained by terminating the polymerization as described above has an acid value of 0.1 to 50 mg-
KOH / g, preferably in the range of 0.1 to 20 mg-KOH / g.
When the acid value is less than 0.1 mg-KOH / g, the resulting polymer has a small number of carboxyl groups, the low-contracting agent is separated during thickening, and the molding surface is contaminated, and the appearance of the molded product is not good. On the other hand, when it exceeds 50 mg-KOH / g, the polymer is precipitated during the polymerization, which is not suitable as a low-shrinking agent.

The unsaturated polyester resin in the present invention is a normal unsaturated polyester resin, and is α, β-
Unsaturated carboxylic acids and polyhydric glycols, or α, β-
It can be easily obtained by polycondensing an unsaturated carboxylic acid, a polyvalent saturated carboxylic acid, and a polyhydric glycol, and dissolving them in styrene and / or methyl methacrylate. A known esterification catalyst such as dibutyltin oxide may be used when polycondensing these.

Here, examples of the α, β-unsaturated carboxylic acid include maleic anhydride, maleic acid, fumaric acid,
Examples thereof include tetraconic acid, itaconic acid, and a mixture of two or more selected from these alkyl esters. As the polyvalent saturated carboxylic acid, for example,
Phthalic anhydride, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, tetrabromophthalic anhydride, het acid, succinic acid,
Examples include adipic acid, sebacic acid, and one kind or a mixture of two or more kinds selected from these alkyl esters.

Examples of the polyhydric glycols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, Dibromoneopentyl glycol, 1,6-hexanediol; alkyl oxide adduct of bisphenol A or bisphenol F such as ethylene oxide or propylene oxide, hydrogenated bisphenol A, hydrogenated bisphenol F, hydrogenated bisphenol A or ethylene oxide of hydrogenated bisphenol F Or alkyl oxide adducts such as propylene oxide; dihydric glycols such as pentaerythrite diallyl ether; trihydric glycols such as trimethylolpropane One type chosen, or a mixture of two or more thereof.

In the present invention, the resulting styrene polymer composition is used as a shrinkage reducing agent in an amount of 2 to 100 parts by weight based on 100 parts by weight of the unsaturated polyester resin. The low-shrinking agent composition and the unsaturated polyester resin include a thickener such as magnesium oxide, a stabilizer,
Mixing fillers, reinforcing materials, thickeners, release agents, pigments, etc.
A sheet molding compound (hereinafter, abbreviated as SMC) or a bulk molding compound (hereinafter, abbreviated as BMC) having good workability can be manufactured. At this time, the amount of the thickener is 100 parts by weight of the total amount of the unsaturated polyester resin and the low-shrinking agent composition,
It is 0.1 to 5 parts by weight. The obtained compound can be formed into a desired molded product by heat compression molding, injection molding, transfer molding, or the like.

Further, not only SMC or BMC but also the low-shrinking agent composition of the present invention has a significantly improved compatibility with unsaturated polyester resin as compared with that of conventional polystyrene. Unsaturated polyester resin in the product, if necessary, a curing agent, a curing accelerator, a stabilizer, a filler, a reinforcing material, a release agent, a pigment, a flame retardant, and the like are appropriately mixed, and a known molding method, The target molded product can be obtained by hand lay-up molding, spray-up molding, resin injection molding, cold press molding, matched die molding, pull-through molding, and filament winding molding.

[0022]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples. In the following, “part” is based on weight.

Example 1 98 parts of styrene, 2 parts of methacrylic acid and 0.25 part of n-DM were placed in a glass four-necked flask (with a stirrer, an external heater, a cooling tube, a thermometer and a nitrogen introducing tube), and a nitrogen stream was introduced. Under stirring, the mixture was heated from room temperature to 100 ° C over 1 hour. Heat from 100 ℃ to 130 ℃ over 1 hour,
Polymerization was carried out at intervals of 0 minutes while measuring the polymerization rate by the nonvolatile method. When the polymerization rate exceeds 40%, dry air is blown into the polymerization liquid and cooling is started, the temperature is lowered to 80 ° C., 0.1 part of hydroquinone as a polymerization terminator is added, and further,
The composition was cooled to 10 ° C. or lower and the polymerization was terminated to obtain a low-shrinking agent composition. The composition has a polymerization rate of 41.2% and a viscosity of 28.
The poise and its acid value were 13.4 mg-KOH / g. These are summarized in Table 1.

Next, SMC was prepared using the composition of the low-contracting agent with the following composition. Unsaturated polyester resin 70 parts (Brand name Esther ML1815, resin for molding, manufactured by Mitsui Toatsu Chemicals, Inc.) Low shrinkage agent composition 30 parts Calcium carbonate 150 parts Zinc stearate 5 parts t-Butyl perbenzoate 1.5 parts Glass Fiber (6 mm length, chopped strands) 167 parts Magnesium oxide 2 parts Black pigment 2 parts This SMC is thickened at 40 ° C for 24 hours and aged, and then press molded (temperature 140 ° C, pressure 100Kg / cm ² , time) 5 minutes) to obtain a molded plate having a thickness of 300 mm × 300 mm × 3 mm. The obtained SMC and molded plate are evaluated by the following methods,
The results are shown in Table 1. -Sheet releasability: After increasing the viscosity of this SMC, the workability in peeling the sheet adhering to the SMC was evaluated in three levels. ○: Workability was good without any stickiness. △: Workability was a little bad with some stickiness. X: Workability was bad with a little stickiness overall. After this SMC was press-molded, the surface of the mold was visually evaluated in three levels. ○: The surface of the mold is not contaminated with resin at all △: Part of the mold is contaminated with resin ×: The entire surface of the mold is contaminated with resin Appearance: The appearance of this molded plate was visually evaluated in three levels. ○ ・ ・ ・ Surface is smooth and glossy △ ・ ・ ・ Surface is partially raised and slightly glossy × ・ ・ ・ Waviness occurs and there is no gloss overall ・ Molding shrinkage ratio: JIS-K- Based on 6911, a disk having a diameter of 90 mm and a thickness of 11 mm was press-molded from this SMC, and the molding shrinkage ratio was determined. Bending strength and elastic modulus: Based on JIS-K-6911, a test piece was cut out from this molded plate and the bending strength and elastic modulus were measured.

Example 2 A low-contraction agent composition was obtained in the same manner as in the first half of Example 1 except that the amount of styrene was changed to 95 parts and the amount of methacrylic acid was changed to 5 parts. The polymerization rate of this composition is 41.4%, its viscosity is 34 poise and its acid value is 3.
It was 3.1 mg-KOH / g. Thereafter, SMC was prepared using this composition in the same manner as in the latter half of Example 1, a molded plate was obtained, and evaluated. The results are shown in Table 1.

Example 3 99 parts of styrene, 1 part of maleic acid and 0.2 part of n-DM were placed in a glass four-necked flask (with a stirrer, an external heater, a cooling tube, a thermometer and a nitrogen introducing tube), and a nitrogen stream was introduced. Under stirring, the mixture was heated from room temperature to 100 ° C. over 1 hour.
Further, the mixture was heated from 100 ° C. to 130 ° C. over 1 hour, and polymerized at 20 minute intervals while measuring the polymerization rate by the nonvolatile content method. When the polymerization rate exceeds 30%, dry air is blown into the polymerization solution and cooling is started, the temperature is lowered to 80 ° C., 0.1 part of the polymerization terminator hydroquinone is added, and further 10
The composition was cooled to below 0 ° C., and the polymerization was terminated to obtain a low-shrinking agent composition. The composition has a polymerization rate of 32.4% and a viscosity of 20 p.
Oise and its acid value were 5.0 mg-KOH / g. Thereafter, SMC was prepared using this composition in the same manner as in the latter half of Example 1, a molded plate was obtained, and evaluated.
The results are shown in Table 1.

Example 4 A glass four-necked flask (with a stirrer, an external heater, a cooling tube, a thermometer and a nitrogen inlet tube) was charged with 99.3 parts of styrene, 0.7 part of acrylic acid and 0.5 part of n-DM, and a nitrogen stream was introduced. Under stirring, the mixture was heated from room temperature to 100 ° C. over 1 hour. Heat from 100 ℃ to 130 ℃ for another hour,
Polymerization was performed at 20-minute intervals while measuring the polymerization rate by the non-volatile method. When the polymerization rate exceeded 45%, dry air was blown into the polymerization solution and cooling was started, the temperature was lowered to 80 ° C, and 0.1 part of the polymerization terminator hydroquinone was added, and
The composition was cooled to 10 ° C. or lower and the polymerization was terminated to obtain a low-shrinking agent composition. The polymerization rate of this composition is 45.8% and its viscosity is 31
The poise and its acid value were 7.8 mg-KOH / g. Thereafter, SMC was prepared using this composition in the same manner as in the latter half of Example 1, a molded plate was obtained, and evaluated.
The results are shown in Table 1.

Example 5 A glass four-necked flask (with a stirrer, an external heater, a cooling tube, a thermometer and a nitrogen introducing tube) was used to prepare 97 parts of styrene, 3 parts of acrylic acid, 1 part of AIBN and t-dodecyl mercaptan ( 0.5 parts of t-DM) is added, and the mixture is heated from room temperature to 70 ° C for 1 hour with stirring under a nitrogen stream and held, and polymerization is performed at 20-minute intervals while measuring the polymerization rate by the nonvolatile content method. Let When the polymerization rate exceeds 25%, dry air is blown into the polymerization solution and cooling is started, and 0.1 part of hydroquinone, a polymerization terminator, is added, cooled to 10 ° C or lower, and the polymerization is terminated to reduce the shrinkage agent composition. I got a thing. The polymerization rate of this composition was 26.8%, its viscosity was 30 poise, and its acid value was 19.0 mg-KOH / g. From this point onward, S was obtained using this composition in the same manner as in the second half of Example 1.
MC was prepared, a molded plate was obtained, and this was evaluated. The results are shown in Table 1.

[0029]

[Table 1]

Comparative Example 1 In the first half of Example 2, when the polymerization rate exceeded 5%, dry air was blown into the polymerization solution and cooling was started,
The temperature was lowered to 0 ° C., 0.1 part of hydroquinone as a polymerization terminator was added, and the mixture was further cooled to 10 ° C. or lower to terminate the polymerization to obtain a low-shrinking agent composition. The polymerization rate of this composition is 6.2%,
Its viscosity is 3.4 poise and its acid value is 13.1 mg-KOH / g
Met. Thereafter, SMC was prepared using this composition in the same manner as in the latter half of Example 1 to obtain a molded plate,
This was evaluated. The results are shown in Table 2.

Comparative Example 2 In the first half of Example 1, the same operation was performed except that the polymerization was not terminated even when the polymerization rate exceeded 40%. When the degree of polymerization exceeded 70%, the viscosity of the polymerization solution became extremely high, stirring was not possible, and a composition could not be obtained.

Comparative Example 3 A low-contraction agent composition was obtained in the same manner as in the first half of Example 2 except that the amount of n-DM was changed to 1.5 parts. The composition has a polymerization rate of 31.9% and a viscosity of 11 p.
Oise and its acid value were 5.1 mg-KOH / g. Thereafter, SMC was prepared using this composition in the same manner as in the latter half of Example 1, a molded plate was obtained, and evaluated.
The results are shown in Table 2.

Comparative Example 4 The same operation was carried out in the first half of Example 2 except that n-DM was not used. Before the rate of polymerization reached 30%, the viscosity of the polymerization solution became extremely high, stirring was not possible, and a composition could not be obtained.

Comparative Example 5 A low-shrinking agent composition was obtained in the same manner as in Example 3, except that acrylic acid was not used.
The composition had a degree of polymerization of 25.9%, a viscosity of 28 poise and an acid value of 0 mg-KOH / g. From this point onward, S was obtained using this composition in the same manner as in the second half of Example 1.
MC was prepared, a molded plate was obtained, and this was evaluated. The results are shown in Table 2.

Comparative Example 6 The same operation was carried out in the first half of Example 1 except that the amount of styrene was changed from 100 parts to 85 parts and 2 parts of methacrylic acid was changed to 15 parts of acrylic acid. Polymerization rate is 10
%, The polymer was precipitated, and it could not be blended, molded, or evaluated as a low-shrinking agent.

[0036]

[Table 2]

[0037]

According to the present invention, the sheet releasability after thickening the compound is good, the molding surface after molding the compound is not contaminated, and the molded product has a low shrinkage ratio and a high mechanical strength. While maintaining the desired strength, its appearance is good.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masanori Sugawara, 1900 Togo, Mobara-shi, Chiba Mitsui Toatsu Chemical Co., Ltd. (72) Inventor Takashi Iiyama 1900, Togo, Mobara-shi, Chiba Mitsui Toatsu Chemical Co., Ltd. ( 72) Inventor Hideo Arikawa 1900, Togo, Mobara-shi, Chiba Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. A chain transfer agent is added in an amount of 0.01 to 1 part by weight per 100 parts by weight of a monomer composition consisting of 90 to 99.9% by weight of styrene and 10 to 0.1% by weight of a polymerizable monomer having a carboxyl group. In addition, bulk polymerization, obtained by stopping the polymerization at a polymerization rate of 10 to 70%, and an acid value of 0.1 to 50 mg-KOH / g, a shrinkage reducing agent composition for unsaturated polyester resins.