JPH023686B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a multilayer reinforced plastic molded product that can eliminate "sink marks" that occur during molding on molded products with ribs or bosses.

Sheet molding compound (abbreviated as SMC) molding materials are generally unsaturated polyester resins, thermoplastic resins, fillers, mold release agents, colorants,
A compound mixed with a curing catalyst, a thickener, etc. is spread on a film, impregnated with glass fibers, and then covered with a film and compressed appropriately to sufficiently impregnate and thicken it to produce a sheet. Also, bulk molding compound (abbreviated as BMC)
The molding material is produced in bulk by kneading glass fiber into these compounds, impregnating it, and thickening it.

When molding large molded products using SMC or BMC molding materials, ribs and bosses are often used for integral molding due to design or productivity issues. In such cases, traditional SMC or
In BMC, so-called "sink marks" occur on the opposite side of the ribs and bosses, impairing the smoothness of the surface. In order to suppress the occurrence of sink marks, conventional techniques have included the addition of various thermoplastic resins or the amount of addition thereof, the unsaturated polyester resin itself, and the molding conditions such as press pressure and press temperature. However, none of these methods has been able to completely suppress the occurrence of sink marks.

In view of these points, the present inventors conducted intensive research on a method for eliminating the occurrence of sink marks on the surface of molded products, and as a result, the present inventors used a molding material containing a foaming agent in the inner layer and achieved this objective by using a two-layer molding method. The inventors have discovered that it is possible to achieve the following, and have completed the present invention.

That is, in the present invention, a thermosetting resin molding material containing a foaming agent is molded, foamed, and hardened in a mold, and then a part of the mold is released, and the foaming agent is removed while the molded product remains in the mold. A multi-layered product characterized by laminating a low-shrinkage or non-shrinkage thermosetting resin molding material with excellent surface smoothness that does not contain any of A method for manufacturing a reinforced plastic molded article is provided.

The molding material referred to in the present invention is a combination of a thermosetting resin typified by unsaturated polyester resin, a fibrous reinforcing material, a thickener, a foaming agent, a curing catalyst, and the like.

The unsaturated polyester resin represented by the thermosetting resin is synthesized by a conventional method, and the raw materials used therefor can be those conventionally used, but are not limited to these.

Unsaturated polyester resins are produced by polycondensation of aromatic saturated dibasic acids or their acid anhydrides, α,β-unsaturated dibasic acids or their acid anhydrides, and glycols; It is obtained by dissolving an unsaturated polyester produced using an aliphatic or alicyclic saturated dibasic acid as a component in an α,β-unsaturated monomer.

Aromatic saturated dibasic acids as acid components of unsaturated polyesters include phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride,
Halogenated phthalic anhydride and esters thereof are used, and aliphatic or alicyclic saturated dibasic acids include succinic acid, adipic acid, sebacic acid,
Hexahydrophthalic anhydride and esters thereof are used.

As the α,β-unsaturated dibasic acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, chlormaleic acid, and esters thereof are used.

Glycols include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-butanediol,
1,4-butanediol, neopentyl glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, bisphenol A, hydrogenated bisphenol A, 2,2-di(4-hydroxypropoxyfluoride) ethylene oxide, which is an oxide,
Propylene oxide and the like are also useful. Each reaction component is not particularly limited to the above substances as long as it can be polycondensed with the unsaturated polyester. Furthermore, the ends of the unsaturated polyester may be further vinyl-modified with glycidyl (meth)acrylate, etc., and (meth)acrylates of bisphenol A glycidyl ether are included in the unsaturated polyester used in the present invention. , a terminal vinyl compound such as (meth)acrylates of polyfunctional alcohols.

The unsaturated polyester has a molecular weight in the range of 1000 to 4000, an acid value in the range of 1 to 50, and a hydroxyl value in the range of 1 to 60. ) When using a terminal vinyl compound such as acrylates, a molecular weight in the range of 100 to 1000 can be used.

The α,β-unsaturated monomer used in the unsaturated polyester resin is generally styrene, but is not limited to styrene, and includes vinyltoluene, α-methylstyrene, chlorostyrene, and methylmethane. Vinyl monomers or vinyl oligomers capable of crosslinking with unsaturated polyesters such as acrylic compounds such as acrylates and allyl compounds such as triallyl cyanurate may be used alone or in combination.

In the unsaturated polyester resin, the appropriate proportion of the unsaturated polyester and the α,β-unsaturated monomer is in the range of 30 to 80 parts by weight of the former and 70 to 20 parts by weight of the latter.

In the molding material of the present invention, a thermoplastic resin as a low shrinkage imparting agent may or may not be mixed.

Examples of thermoplastic resins include polystyrene,
Examples include polyethylene, polyacrylate, polyvinyl acetate, and saturated polyester, which may be used alone or in combination. The amount of these thermoplastic resins used is 0 to 100 parts by weight per 100 parts by weight of the unsaturated polyester resin.

In addition, examples of fillers used include calcium carbonate, aluminum hydroxide, kaolin, barium sulfate, and the like. The amount used is 50 to 200 parts by weight per 100 parts by weight of the unsaturated polyester resin.

As curing catalysts, organic peroxides usually used for unsaturated polyester resins, such as benzoyl peroxide, t-butyl perbenzoate,
Examples include di-t-butyl hydroperoxide, dikyumyl peroxide, and t-butyl peroctate. The amount used is 0.5 to 5 parts by weight per 100 parts by weight of the unsaturated polyester resin, but in some cases, a known curing accelerator may be used in combination.

As thickeners, alkaline earth metal oxides,
In addition to inorganic thickeners such as hydroxides, organic thickeners such as polyisocyanate types can be used. The amount used is unsaturated polyester resin
0.1 to 20 parts by weight are used per 100 parts by weight.

As the mold release agent, any release agent used in conventional unsaturated polyester resins may be used, but zinc stearate is preferably used.

In addition to these, colorants, additives for curing adjustment, etc. may be added, but those used in conventional unsaturated polyester resins are used.

As fibrous reinforcing materials, glass fibers such as chopped strands, chopped strand mats, and roving cloth, carbon fibers, natural fibers, synthetic fibers, etc. are used, but these are not suitable for the final use of molded products. Therefore, it is selected appropriately.

The blowing agents used in the molding material of the present invention include, as organic blowing agents, azo compounds such as azobisisobutyronitrile, azodicarbonamide, 2-t-butylazo-2-methoxy-4-methylpentane; toluenesulfonyl hydrazide,
There are hydrazine blowing agents such as 4,4'-oxybisbenzenesulfonyl hydrazide and ditrosopentamethylenetetramine, and examples of inorganic blowing agents include sodium hydrogen carbonate. The amount of these blowing agents used is 0.01 to 10 parts by weight per 100 parts by weight of the unsaturated polyester resin.
Foam stabilizers, foaming aids, etc. may be added alone or in combination.

Molding of a thermosetting resin molding material is generally carried out at a molding temperature of 60 to 180°C and a molding time of 0.5 to 20 minutes, but this can be changed as appropriate depending on the type of thermosetting resin.

The most suitable molding method is press molding, but injection molding and transfer molding may also be used.

In the method of the present invention, the foamed FRP is molded in the first step, a part of the mold is released while the molded product remains in the mold, and in the second step, a non-foamable molding material is charged and the mold is released. The non-foamed FRP is laminated on top of the foamed FRP molded product obtained in the first step by pressing with a mold.
Obtain a multilayered FRP molded product.

According to the method of the present invention, the adhesion between the layers is extremely good and there is no possibility of peeling.

By the manufacturing method of the present invention, industrial goods, panels, tanks, housing equipment, automobile parts, etc. can be manufactured.

Next, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In addition, parts in the text indicate parts by weight.

Example 1 Maleic anhydride 196g (2 mol), phthalic anhydride
148g (1 mol), propylene glycol 228g
(3 mol) was heated and dehydrated and condensed at 200° C. in an inert gas stream to obtain an unsaturated polyester having an acid value of 35 and a hydroxyl value of 25. 70 parts of the obtained unsaturated polyester was dissolved in 30 parts of styrene to obtain an unsaturated polyester resin with a viscosity of 17 poise. Add 0.1 part of azobisisobutyronitrile to 100 parts of this unsaturated polyester resin, perform roll kneading, and after confirming that the azobisisobutyronitrile is sufficiently dispersed, add styrene to polystyrene (molecular weight, 26,000). 30 parts of solution (50% concentration) were mixed. Next, 120 parts of calcium carbonate, 5 parts of zinc stearate, 10 parts of cream colorant, and 1 part of t-butyl perbenzoate.
1.5 parts of magnesium oxide and 15 parts of styrene were kneaded, and the resulting compound was used in an SMC impregnating machine to produce a 1-inch SMC having a glass roving chop content of 30%. The SMC was wound into a roll and aged for 24 hours to produce an SMC molding material.

This SMC molding material was suitably cut and molded in the first stage at 50 kg/cm ² for 2 minutes in a mold heated to 140°C. On the other hand, an SMC molding material was prepared by removing the blowing agent azobisisobutyronitrile from this SMC molding material, and second-stage molding was performed to cover the molded article.

The finished molded product having ribs and bosses had excellent surface smoothness, had no "sink marks" on the opposite side of the ribs and bosses, and had excellent adhesion between both layers.

Example 2 450 g (5 mol) of maleic anhydride, 313 g (4.12 mol) of propylene glycol, and 330 g (1 mol) of bisphenol A ethylene oxide adduct (bisphenol A/ethylene oxide = 1/2.3) in an inert gas stream. Then, heat dehydration condensation at 200℃,
55 parts of unsaturated polyester having an acid value of 35 and a hydroxyl value of 27 were dissolved in 45 parts of styrene to obtain an unsaturated polyester resin having a viscosity of 8 poise.

0.1 part of para-toluenesulfonyl hydrazide was kneaded into 100 parts of the obtained unsaturated polyester resin using a roll, and after confirming that it was dispersed, a styrene solution (concentration of polystyrene (molecular weight 200,000)
30%) 30 parts, 120 parts of calcium carbonate, 5 parts of zinc stearate, 1 part of t-butyl perbenzoate,
1.5 parts of magnesium oxide and 5 parts of styrene were kneaded to obtain an SMC compound.

The obtained compound is processed by SMC impregnating machine.
1 inch glass roving tip content 30%
manufactured SMC. After winding up into a roll,
It was aged for 24 hours to obtain an SMC molding material. This SMC
The molding material was suitably cut and molded in the first stage at 60 kg/cm ² for 2 minutes in a mold having ribs and bosses heated to 140°C. On the other hand, this
An SMC molding material was prepared by removing the blowing agent paratoluenesulfonyl hydrazide from the SMC molding material, and molded to cover the molded article.

The finished molded product had excellent surface smoothness, had no "sink" on the opposite side of the ribs and bosses, and had excellent adhesion between both layers.

Example 3 166 g (1 mol) of isophthalic acid, maleic anhydride
196g (2 moles), propylene glycol 228g
(3 mol) was subjected to dehydration condensation under heating at 200° C. in an inert gas stream, and 70 parts of unsaturated polyester having an acid value of 30 was dissolved in 30 parts of styrene to obtain an unsaturated polyester resin having a viscosity of 30 poise. 100 parts of this unsaturated polyester resin, 30 parts of a styrene solution (concentration 50%) of polystyrene (molecular weight 26,000), and 180 parts of calcium carbonate.
1 part, 6 parts of zinc stearate, 1 part of t-butyl perbenzoate, 0.1 part of azodicarbonamide, 1.5 parts of magnesium oxide, and 5 parts of styrene were kneaded in a kneader, and after confirming that they were sufficiently kneaded, 85 parts of glass chopped strands (strand length: 13 mm) were added and thoroughly kneaded. The obtained molding material was covered with Poval film and aged for 24 hours to obtain a BMC molding material.

Ribs heated to 140℃ using this BMC molding material,
The first stage of molding was performed in a mold having a boss at a pressure of 50 kg/cm ² for 2 minutes. On the other hand, a BMC molding material was prepared by removing the blowing agent azodicarbonamide from this BMC molding material, and molding was carried out under the same conditions as in the first stage to cover the molded article. The finished molded product had no sink marks on the opposite side of the ribs and bosses. Moreover, the adhesion between both layers was good.

Comparative Example 1 The SMC molding material of Example 1, which does not contain a blowing agent, was
A two-stage molding method was performed in the same manner as in Example 1.
As a result, "sink marks" were observed on the ribs and bosses of the molded product, and both layers easily peeled off due to impact.

Comparative Example 2 The SMC molding material of Example 2, which does not contain a blowing agent, was
Two-stage molding was performed in the same manner as in Example 2. As a result, sink marks were observed on the ribs and bosses of the molded product.

Claims (1)

[Claims] 1. A thermosetting resin molding material containing a blowing agent is molded in a mold, foamed, and cured, and then a part of the mold is released, and while the molded product remains in the mold, a thermosetting resin molding material that does not contain a blowing agent is heated. A method for manufacturing a multilayer reinforced plastic molded article, which comprises laminating a curable resin molding material on the molded article, pressing it again with a released mold, molding, and curing it.