JPH09241306A - Acrylic SMC manufacturing method - Google Patents

Abstract

(57) [Abstract] [Problem] Acrylic SM that is excellent in handleability, moldability in molding, and obtains a molded article having excellent durability.
Provide C. SOLUTION: A void is provided between two facing parallel plates, a resin sheet is placed in the void, and then an unsaturated monomer mixture containing a polymerization initiator is injected to fill the void. Then, the resin sheet is swollen with an unsaturated monomer mixture.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an acrylic SMC. More specifically, the present invention relates to a method for producing an acrylic SMC that is excellent in handleability, has good moldability in molding, and can obtain a molded article having excellent durability.

[0002]

2. Description of the Related Art Fiber reinforced plastics (FRPs) utilize their light weight and high strength to make use of boats, septic tanks, tanks,
It is used in various applications such as bathtubs, corrosion-resistant equipment, industrial components, automobiles and electrical components. Among FRP, materials that can be compression-molded in the mold, such as sheet molding compound (SMC), are easy to integrally mold, the molding speed is fast, and it can contribute to the improvement of working environment. Replaces materials and spray-up molding materials.

Although conventional SMCs containing unsaturated polyester as a resin component are excellent in moldability and strength, there are problems in surface smoothness, coatability and weather resistance, and various methods are available to solve these problems. Proposed. One of the methods is to replace the resin component of SMC with an unsaturated polyester resin with an acrylic resin. For example, in JP-A-60-226511, a half-life of 10 hours is calculated with respect to 100 parts by weight of a monomer mixture consisting of 60 to 100% by weight of methyl methacrylate and 40 to 0% by weight of a copolymerizable vinyl monomer. 0.01 to 0.4 parts by weight of a radical polymerization initiator (A) having a temperature of 50 ° C. or lower, and a radical polymerization initiator (B) having a 10-hour half-life temperature of 70 ° C. or higher.
Disclosed is a method for producing a methacrylic resin sheet molding material, which comprises adding 0.1 to 1.0 part by weight and polymerizing by heating to make the polymerization rate 40 to 70%.

[0004]

In the polymerization of methyl methacrylate, there is a phenomenon called gel effect that causes a remarkable increase in the polymerization rate with an increase in the polymerization rate, and it is extremely difficult to terminate the polymerization at a desired polymerization rate. Have difficulty. The method described in JP-A-60-226511 adopts a method of polymerizing a mixture of vinyl-based monomers mainly composed of methyl methacrylate to a polymerization rate of 40 to 70%. In the examples of the publication, polymerization is carried out by heating, an exothermic peak at the time of polymerization is observed, and cooling is carried out in the middle to obtain a methacrylic resin sheet molding material having a desired polymerization rate. However, in this method, it is indispensable to observe the polymerization peak, and further, there is a problem that the polymerization rate is sensitively changed with respect to the amount of the polymerization initiator to be added and fluctuation of the polymerization temperature. Furthermore, since the polymerization rate is high under the condition that the polymerization peak is observed, there is a problem that if the cooling rate is different, the polymerization rate of the obtained product is affected.

In view of such circumstances, the present inventor diligently studied an acrylic SMC which is excellent in handleability, has good moldability in molding, and can obtain a molded article having excellent durability. As a result, a resin sheet is provided between parallel plates. Was found, by injecting an unsaturated monomer mixture, and swelling the resin sheet with the unsaturated monomer mixture, it was found that an acrylic SMC having excellent handleability and good moldability can be obtained, The present invention has been completed.

[0006]

Means for Solving the Problems That is, the present invention provides a void between two parallel plates facing each other, installs a resin sheet in the void, and then adds a polymerization initiator to fill the void in the void. A method for producing an acrylic SMC, which comprises injecting an unsaturated monomer mixture contained therein and swelling the resin sheet with the unsaturated monomer mixture. Hereinafter, the present invention will be described in detail.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The resin sheet in the present invention means a sheet containing a polymer mainly containing methyl methacrylate, and the polymer mainly containing methyl methacrylate occupies 80% by weight or more of the sheet. In addition to the conventional methyl methacrylate resin sheet, a sheet containing a filler, a fiber reinforcing material, etc. can be used. Further, the sheet contains a colorant, a light diffusing agent, a release agent, an antistatic agent, a flame retardant, an ultraviolet absorber, an antioxidant, an impact resistance improver, etc., if necessary. Can also be used.

The polymer mainly containing methyl methacrylate is a polymer of an unsaturated monomer mainly containing methyl methacrylate, and the unsaturated monomer mainly containing methyl methacrylate is methyl methacrylate. Of 50% or more and mixed with another unsaturated monomer copolymerizable with methyl methacrylate.

Examples of the filler include, but are not limited to, aluminum hydroxide, aluminum oxide, calcium carbonate, calcium silicate, calcium sulfate, magnesium hydroxide, silica, talc, clay and bentonite. is not. When an artificial marble-like appearance is desired, it is preferable to use aluminum hydroxide, magnesium hydroxide, silica or the like. These inorganic powders can be used not only in one kind but also in two or more kinds in combination.

Examples of the fiber reinforcing material include glass fiber, boron fiber, carbon fiber, polyamide fiber, vinylon fiber, polyester fiber and natural fiber. The amount of the fiber reinforcing agent can be appropriately selected according to the physical properties required for the obtained SMC. It is also possible to use these fibers by subjecting them to a surface treatment or the like in advance to improve the adhesion to the resin.

The unsaturated monomer mixture in the present invention means a mixture of a radically polymerizable unsaturated monomer and an additive, and swells the resin sheet. Examples of the radically polymerizable unsaturated monomer include esters of methacrylic acid or acrylic acid with aliphatic, aromatic or alicyclic alcohols, (meth) acrylic monomers such as hydroxyalkyl esters, and styrene. Monomers, monofunctional unsaturated monomers such as acrylonitrile and vinyl acetate; allyl methacrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate,
Polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,3
-Butylene glycol di (meth) acrylate, 1,6
-Hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, divinylbenzene, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, etc. Examples thereof include polyfunctional unsaturated monomers having a plurality of radical-polymerizable double bonds in the molecule.

Depending on the type of unsaturated monomer, the sheet may not be able to swell by itself, and therefore these unsaturated monomers are usually used in combination of two or more. In particular, when the resin component contained in the sheet has a methyl methacrylate unit as a main component, it is preferable to contain methyl methacrylate in the unsaturated monomer. The type and amount of the monomer used can be determined by trial and error based on the physical properties required for the SMC to be obtained and the ease of swelling.

The additives are those added to the unsaturated monomer as required, and include a polymerization inhibitor, a polymerization inhibitor, a polymer,
It means a colorant, a release agent, a light diffusing agent, an antistatic agent, a flame retardant, an ultraviolet absorber, an antioxidant and the like.

The polymerization inhibitor can be added for the purpose of improving the storage stability of the SMC obtained in the present invention or so that the polymerization does not start at the time of swelling. Examples of the polymerization inhibitor used include hydroquinone, hydroquinone monomethyl ether, 2,2-diphenyl-1-picrylhydrazyl, 4-hydroxy-2,2,6,6-tetramethylpiperazyl-1-oxyl and the like. Can be mentioned.

The amount of the polymerization inhibitor added depends on the kind of the polymerization initiator, the amount added and the kind of the polymerization inhibitor used.
Generally, it is necessary to make the amount of the polymerization initiator smaller than the amount of radicals generated by decomposition at the molding temperature. If the amount of the polymerization inhibitor to be added is too large, the polymerization and curing will not be sufficiently performed during molding, or the polymerization and curing will take a long time, which is not preferable.

When the polymer is added, it may be contained in an amount not exceeding 30% by weight of the unsaturated monomer mixture. As the colorant, a dye, a pigment or the like can be used. As the release agent, a known release agent such as a metal salt of stearic acid such as zinc stearate or aluminum stearate, a fluorine-based release agent, or a silicon-based release agent can be used. In addition, known materials such as a light diffusing agent, an antistatic agent, a flame retardant, an ultraviolet absorber, and an antioxidant can be added.

A polymerization initiator necessary for polymerizing and curing the unsaturated monomer swollen during the molding of SMC is added to the unsaturated monomer. As the type of the polymerization initiator, a known polymerization initiator used in radical polymerization can be used, but since the polymerization does not start during swelling, the 10-hour half-life temperature is higher by at least 10 ° C. or more than the temperature during swelling. Select one to use. The amount of the polymerization initiator to be added is generally 0.001 to 5 parts by weight with respect to 100 parts by weight of the unsaturated monomer mixture to be swollen.

The two facing plates in the present invention are containers for forming voids. After swelling the unsaturated monomer, these two facing plates are removed to remove the acrylic resin. Get the SMC. Therefore, the material is not particularly limited as long as it is not dissolved in the unsaturated monomer, and glass, stainless steel or the like is used. Further, the shape thereof is not limited to an ordinary flat plate, and a continuous belt can be used to improve productivity. If a release film is installed in advance on the void side of the plate, that is, the side in contact with the unsaturated monomer, an acrylic SMC whose surface is protected can be easily obtained after swelling on the resin sheet, which is convenient. Is.

The manufacturing method of the present invention will be described below. First, an air gap is created using two plates and a gasket having a thickness corresponding to the desired air gap. The resin sheet is inserted into this. The resin sheet may be inserted through the opening after forming the voids, or may be previously placed on the plate forming the voids in advance. Alternatively, it is possible to insert the resin sheet after injecting the unsaturated monomer mixture into the voids.

The sheets installed in the voids are selected so that the volume thereof is 30 to 95% of the volume of the voids. To do this, make the projected areas of the sheet and void the same,
It can be easily adjusted by setting the thickness of the sheet used to 30 to 95% of the thickness of the voids. Seat volume is 3
If it is less than 0%, the resulting SMC will be extremely sticky and the handling will be poor. Conversely, if the volume of the sheet exceeds 95%, it will not be possible to swell the sheet uniformly with the unsaturated monomer mixture. However, the fluidity of the obtained SMC is not uniform, which is not preferable.

An unsaturated monomer mixture is injected into the void so as to fill the void, and after the injection, the inlet is sealed and swelling is performed. The unsaturated monomer mixture to be injected is preferably degassed in advance so that the polymerization and curing at the time of subsequent molding is not hindered by dissolved oxygen and the like.

The conditions for swelling depend on the components of the unsaturated monomer mixture used, but are generally in the temperature range of room temperature to 70 ° C. and in the range of several hours to 48 hours. In this case, the added polymerization initiator does not start the polymerization and curing of the unsaturated monomer, the type of the polymerization initiator, the amount, and the type of the polymerization inhibitor,
Set the conditions by considering the amount. After swelling, the plate forming the void is removed to obtain an acrylic SMC.

The acrylic SMC of the present invention is compression molded in a mold to obtain a molded product. Conditions for molding using the molding material of the present invention include a temperature range of 80 to 150 ° C.,
It may be carried out in a pressure range of 1 to 200 kg / cm ² .
Good fluidity cannot be obtained at temperatures lower than 80 ° C.
Polymerization at a temperature higher than 50 ° C. is not preferable because not only the polymerization reaction but also the decomposition due to the depolymerization reaction or the problem of coloration due to high temperature occurs. The acrylic S of the present invention
When molding MC, for example, by using together with SMC or BMC made of unsaturated polyester or other resin, lamination,
It may be combined.

[0024]

INDUSTRIAL APPLICABILITY The acrylic SMC of the present invention is excellent in handleability, can be easily produced, has good moldability in molding, and is excellent in durability.

[0025]

EXAMPLES The present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. [Measurement of Content of Polymer] 20 g of acrylic SMC was added.
After being dissolved in 100 ml of acetone, it was poured into 100 ml of methanol to reprecipitate and separate the polymer component. The precipitate was filtered out, dried under reduced pressure, and then weighed to determine the polymer content. In the case of containing a filler or a fiber reinforcing agent, the filler or the fiber reinforcing agent is filtered off when dissolved in acetone, and the filtrate is subjected to the same operation as above to determine the content of the polymer. It was

Example 1 A soft polyvinyl chloride tube was separated on two glass plates (size 30 × 30 cm, thickness 1 cm) having a 250 μm-thick polyethylene terephthalate film on one surface as a release film. It was sandwiched so that the mold film surface was the inner surface, and a cell having a gap of 3.7 mm in thickness was produced. A 25 x 25 cm methacrylic resin sheet with a thickness of 2 mm (SUMIPEX Sumitomo Chemical Co., Ltd.)
Manufactured).

Further, methyl methacrylate 100 is placed in the voids.
Based on parts by weight, polymerization initiator Trigonox 22-B75
A monomer mixture prepared by mixing 0.19 parts by weight of Kayaku Akzo Co., Ltd. was injected, and the injection port was closed. This cell was held in a hot air drying oven at 60 ° C. for 15 hours, then allowed to cool to room temperature, the glass plate was removed, and an acrylic SMC having a release film on the surface layer was obtained. The resulting acrylic SMC was flexible and had almost no stickiness on the surface.
The polymerization rate was 53.1%.

Next, the width is 5 cm, the length is 12 cm, and the depth is 4 c.
The obtained acrylic SMC was placed in a box-shaped molding die of m, and press-molded for 5 minutes under the conditions of a temperature of 140 ° C. and a pressure of 120 kg / cm ² to prepare a molded body. The obtained molded product was transparent and had a good appearance.

Example 2 An acrylic SMC was obtained in the same manner as in Example 1 except that the vinyl chloride tube used was changed to make the void thickness 5.1 mm. The resulting acrylic SMC is flexible,
There was almost no stickiness on the surface. The polymerization rate was 39.1%. In addition, as a result of producing a molded body in the same manner as in Example 1, a transparent molded body having a good appearance was obtained.

Example 3 80 parts by weight of methyl methacrylate and aluminum hydroxide (CW-325 manufactured by Sumitomo Chemical Co., Ltd.) 12 were placed in a flask.
0 parts by weight was added, and the mixture was thoroughly stirred and mixed. Further, 0.2 parts by weight of azobisisobutyronitrile was added as a polymerization initiator, dissolved by stirring, and then defoamed under reduced pressure to obtain an acrylic syrup. A cell was prepared by using two glass plates and a vinyl chloride tube so that the gap had a thickness of 2.1 mm, and the above acrylic syrup was injected into the cell, and the injection port was closed. Put the injected cell in the hot air drying oven, and
Polymerization of the acrylic syrup was carried out by holding at a temperature of 0 ° C. for 12 hours and further at a temperature of 120 ° C. for 2 hours. After cooling, the two glass plates were removed to obtain an artificial stone-like plate.

An acrylic SMC was obtained in the same manner as in Example 1 except that the plate obtained by the above method was used instead of the methacrylic resin sheet. The resulting acrylic SMC was flexible and had almost no stickiness on the surface. The polymerization rate was 34.9%. In addition, as a result of producing a molded body in the same manner as in Example 1, a white molded body having a good appearance of artificial stone substitute was obtained.

Example 4 200 parts by weight of methyl methacrylate and 0.2 parts by weight of azobisisobutyronitrile were placed in a flask and dissolved by stirring.
Defoaming was performed under reduced pressure to obtain an acrylic syrup. The thickness of the void is 3.6 by using two glass plates and a vinyl chloride tube.
A cell was prepared so as to have a size of mm. Glass fibers were spread in the cell. The above acrylic syrup was injected into this, and the injection port was closed. After the injection, the cell was placed in a hot air drying oven and kept at a temperature of 60 ° C for 12 hours, and
Polymerization of the acrylic syrup was carried out by holding at a temperature of 20 ° C. for 2 hours. After cooling, the two glass plates were removed to obtain a glass fiber-containing acrylic resin plate.

An acrylic SMC was prepared in the same manner as in Example 1 except that the plate obtained by the above method was used in place of the methacrylic resin sheet, and the vinyl chloride tube used was changed to make the void thickness 5.1 mm. Got The resulting acrylic SMC was flexible and had almost no stickiness on the surface. The polymerization rate was 57.7%. As a result of producing a molded body in the same manner as in Example 1, a molded body containing glass fibers and having a good appearance was obtained.

Claims (3)

[Claims] 1. A void is provided between two facing parallel plates, a resin sheet is placed in the void, and then an unsaturated monomer mixture containing a polymerization initiator is filled so as to fill the void. A method for producing an acrylic SMC, which comprises injecting and swelling the resin sheet with an unsaturated monomer mixture. 2. The resin sheet is a sheet containing a polymer mainly containing a methyl methacrylate unit as a main component.
The manufacturing method as described. 3. The production method according to claim 1, wherein the unsaturated monomer is methyl methacrylate.