JPH09174676A - Manufacture of acrylic product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent expansion of flaw due to heat return by molding with heat at a specified temperature an acrylic resin sheet to be obtained by adding specified quantities of a crosslinker and polymerization initiator to a syrup, holding it in a specified temperature and time, cooling it slowly at a specified cooling speed, and reinforcing it with a reinforced resin material. SOLUTION: A part of a mixture of methyl methacrylate itself or 94wt.% or above of it and 6wt.% or below of acryl ester is polymerized so as to produce a syrup. When the syrup is to be treated with heat by adding a crosslinker and a polymerization initiator in it and when [η] of a sheet which is completely polymerized under the absence of the crosslinker is A(1/g), and in a case of 0.05<=A<=0.10, in a case of 0.5-4<=A<=B<=0.9-4×A, 0.10<=A<=0.20, a value of B to be limited by 0.02<=B<=0.9-4×A is made to be loadings of the crosslinker. The obtained acrylic resin sheet is molded with heat at a temperature of 180-200 deg.C, held at 75-80 deg.C for 1.5hours or longer. Thereafter, it 18 cooled slowly at a cooling rate of 15 deg.C/hr and reinforced by a reinforced resin material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an acrylic product such as an acrylic bathtub which is less likely to be remolded by heating.

[0002]

2. Description of the Related Art Conventionally, in the case of heating a thermoplastic sheet of acrylic resin or the like and performing thermoforming such as vacuum or compressed air, various prescriptions have been studied in order to improve the formability. For example, there is a method for producing an acrylic resin sheet having excellent thermoformability and solvent resistance (Japanese Patent Publication No. 6-70098), and a sheet is devised to obtain a desired shape of a molded article having a complicated shape more uniformly. Has been done.

[0003]

When such a molded article of an acrylic resin sheet is used in a product used under high temperature water such as a bathtub, when the molded article is exposed to a temperature of 80 ° C. or higher, the molded article becomes The force of returning to the original shape acts, causing a phenomenon in which the shape is deformed (hereinafter referred to as “heating return”).

With respect to this heating return, as seen in the acrylic bath, there is no change in the overall shape of the one reinforced with a reinforced resin material or the like. However, there is a risk of serious defects in the appearance such as scratches on the surface of the molded product and damage to the edges of the sheet, even if they are reinforced, the scratches will expand or the edges will shrink and cause peeling. There is. That is, according to the study by the present inventors, when the surface of the acrylic bath has a scratch with a depth of more than 0.05 mm, the scratch may spread in about 1 hour when exposed to hot water exceeding about 80 ° C. It's known.

Although such a phenomenon has not been a problem in Western countries where there is no custom of additional cooking, it has become a problem with the spread of acrylic bathtubs in Japan.

An object of the present invention is to provide an acrylic resin product in which the expansion of scratches due to the return of heat is less likely to occur.

[0007]

The gist of the present invention is to provide a polymerization initiator and a chain transfer agent to methyl methacrylate alone or to a monomer mixture of 94% by weight or more of methyl methacrylate and 6% by weight or less of an acrylate ester. To partially polymerize to produce a syrup, and then to the obtained syrup, a cross-linking agent and a polymerization initiator are added and heat treatment is performed to thermoform an acrylic resin sheet obtained by cast polymerization. In the method of obtaining an acrylic product that is reinforced with a reinforced resin material, in the process of cast polymerization performed by adding a crosslinking agent and a polymerization initiator to the syrup and then heat-treating, complete polymerization is performed in the absence of the crosslinking agent. [Η] of the made sheet is A
(l / g) (1) 0.05 ≤ A <0.10 0.5-4 x A ≤ B ≤ 0.9-4 x A (1) (2) 0.10 ≤ A ≤ 0.20 0.02 ≤ B ≤ 0.9-4 x A ... B limited by the ranges of formulas (1) and (2) expressed by (2)
Use the acrylic resin sheet obtained by the formula in which the value of is the addition amount (% by weight) of the cross-linking agent.
Thermoforming in the temperature range of 0 to 200 ° C, then holding at a temperature of 75 to 80 ° C for 1.5 hours or more and then 15 ° C per hour
A method for producing an acrylic product is characterized in that the molding strain at the time of thermoforming is removed by gradually cooling at the following cooling rate, and then the reinforcing product is reinforced.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing an acrylic product of the present invention comprises producing a syrup, casting polymerization of the syrup in a mold to produce a sheet, and thermoforming the sheet to obtain a molded article. It is reinforced with a reinforced resin material.

In the syrup production process, methyl methacrylate alone or a monomer mixture of 94% by weight or more of methyl methacrylate and 6% by weight or less of acrylic acid ester is polymerized in the presence of a chain transfer agent and a polymerization initiator.

Examples of the acrylate ester used for mixing and copolymerizing with methyl methacrylate in the production of syrup include methyl acrylate, ethyl acrylate, n-butyl acrylate and 2-ethylhexyl acrylate. These may be used alone or in combination of two or more.

The use of acrylic ester is used to improve the thermoformability of the sheet, the adhesion to the reinforced resin material, and the like. The amount used varies depending on each Tg, 6% by weight or less. If it exceeds 6% by weight, the heating return becomes too large. From the viewpoint of suppressing heating back, methyl methacrylate alone is desirable.

The chain transfer agent used in the present invention includes
Examples include alkyl mercaptans, aromatic mercaptans, thioglycolic acid esters, β-mercaptopropionic acid esters, and the like. These can be used alone or in combination of two or more. The amount of chain transfer agent used is
The range varies depending on the chain transfer constant, but the amount of simple substance is 100% by weight
On the other hand, it is about 0.01 to 2.0% by weight, preferably about 0.01 to 0.70% by weight. If it is too small, the degree of polymerization of the polymer will be high, making it difficult to perform high-stretching molding, and if it is too large, the molecular weight will be small and the mechanical strength will be reduced, and the polymerization rate will be greatly delayed. In terms of polymerization rate,
It is advantageous that the amount of the chain transfer agent is small and the chain transfer constant is large.

The polymerization initiator used in the present invention includes:
Lauroyl peroxide, benzoyl peroxide, di-isopropyl peroxydicarbonate, di-n-
Peroxides such as butyl peroxydicarbonate, 2,2'-azobis (isobutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 1,1'-azobis (cyclohexane- 1-carbonitrile), azobis (2,4
And azo compounds such as dimethyl 4-methoxyvaleronitrile). These may be used alone or in admixture of two or more. The amount of the polymerization initiator used is about 0.001 to 0.50% by weight based on 100% by weight of the monomer.

The syrup is produced by mixing a mixture of the above monomer, chain transfer agent and polymerization initiator at a temperature of about 60 to 120 ° C.
Perform up to a polymerization rate of about 50%. As a reactor used for producing the syrup, a known reactor such as a tubular reactor or a tank reactor can be used, and the reactor can be batch or continuous.

In the process of producing a sheet by cast polymerization by adding and mixing a crosslinking agent and a polymerization initiator to the obtained syrup, [η] of the sheet completely polymerized under the condition that the crosslinking agent is not present is A (l / g) (1) 0.05 ≤ A <0.10 0.5-4 x A ≤ B ≤ 0.9-4 x A (1) (2) 0.10 ≤ A ≤ 0.20 0.02 ≤ Polymerization is carried out with the value of B defined by the formulas (1) and (2) represented by B ≦ 0.9-4 × A (2) defined as the amount of the crosslinking agent added (% by weight). This limited range refers to the shaded area in FIG.
In the present invention, when [η] is smaller than the lower limit of the shaded area in FIG. 1, the solvent resistance is poor, and when it is larger than the upper limit of the shaded area in FIG. 1, the heating reversion is large. Too much and the moldability also deteriorates.

Examples of the cross-linking agent used in the present invention include glycol dimethacrylates, glycol diacrylates, diol dimethacrylates, diol diacrylates, polyfunctional methacrylates, polyfunctional acrylates, and the like. I don't. These crosslinking agents can be used alone or in combination of two or more. Regarding the amount of use, when it is smaller than the lower limit of the shaded area in FIG. 1, the effect of elongation uniformity by the elongation cross-linking agent cannot be obtained, and when it is larger than the upper limit of the shaded area in FIG. , The heating return becomes too large.

The term [η] as used herein means that the material is dissolved in a chloroform solution to give a solution of about 0.1% by weight, and the flow time t between the marked lines of the Ostwald viscometer and the flow down time t of the chloroform are t.
0 is measured at 25 ° C. and [η] is calculated from the following equation.

[0018]

[Equation 1]

As the polymerization initiator used in the cast polymerization, the polymerization initiator described in the production of syrup can be used, and the amount thereof is in the range of 0.01 to 0.50% by weight based on the total amount of syrup.

As a mold used for producing the sheet in the present invention, a mold made of glass, a chrome-plated metal plate, a stainless steel plate or the like and a soft vinyl chloride gasket, and a mold running in the same direction at the same speed. One example is a mold composed of opposed surfaces of a pair of endless belts and continuous gaskets running on both sides of the endless belts at the same speed.

[0021] Casting polymerization is carried out at 40 to 90 ° C as the first polymerization.
0.2 to 10 hours, then 90 to 150 as second polymerization
It can be achieved by performing the treatment at a temperature of about 0.05 to 4 hours.

In the production method of the present invention, a colorant, a plasticizer, a release agent, a stabilizer, a filler and the like can be added if necessary.

Next, the thermoforming, annealing, and reinforcement of the resin sheet with a reinforcing resin will be described. Thermoforming of the obtained resin sheet is performed in a temperature range of 180 to 200 ° C. When molding is performed at a temperature lower than this temperature range, the proportion of the plastic component in the resin sheet decreases, and the heating return increases. Also, when molding at a temperature higher than this temperature range,
Not only is it accompanied by troubles such as foaming, but also the production cost increases, such as the molding time becoming longer.

The thermoformed molded article is further annealed to further eliminate molding strain. The annealing treatment is carried out by leaving the molded product in a uniform environment at a temperature of about 75 to 80 ° C. for 1.5 hours or more, and then slowly cooling it. Hold temperature is 75 ℃
If it is lower than 80 ° C, the effect of annealing cannot be obtained, and if it is higher than 80 ° C, the deformation of the molded product due to heating increases. If the holding time is short, the effect of annealing cannot be obtained. The slow cooling is performed at a cooling rate of 15 ° C or less per hour. If the cooling rate is too fast, cooling distortion will remain. By this annealing treatment, it is preferable to remove the molding strain generated during thermoforming to 30% or less.

For the reinforcement by the reinforcing resin material in the present invention, known polymerization-curable resin raw materials can be used. As the material for the polymerization-curable resin, unsaturated polyester resin, acrylic resin, vinyl ester resin, urethane resin, epoxy resin, and resins obtained by modifying these can be used, and also include foamed resin. Examples of the unsaturated polyester resin include iso type, tele type or bis type unsaturated polyester resins and acrylic modified unsaturated polyester resins thereof, or unsaturated type obtained by adding acrylic resin to the iso type, tele type or bis type unsaturated polyester resins. Select from at least one type of polyester resin. Moreover, you may use glass fiber, a filler, etc. as needed.

As a method for reinforcing the reinforced resin material in the present invention, a known method is used, and it can be carried out by means such as hand layup, spray up, RTM and the like.

According to a study by the present inventors, during the production of the above-mentioned sheet, the ratio of acrylic acid ester in the resin composition of the sheet, the amount of the crosslinking agent added, the intrinsic viscosity [η] (in the absence of the crosslinking agent, It has been found that the reduced viscosities of the sheets when polymerized independently affect the heating return of the acrylic resin sheet molded at a certain temperature.

Acrylate ester ratio Tg is low When the ratio of acrylic acid ester is high, the heat distortion temperature of the sheet is lowered and the formability is improved, but the temperature at which heat reversion occurs is also low, and when heated at the same temperature. The heating return of is large. Especially when it exceeds 6%, the heating return becomes too large.

Addition amount of cross-linking agent The addition of the cross-linking agent improves the solvent resistance, but expands the rubber elastic region and increases the heating return. Although depending on the type of the cross-linking agent, if the amount of the cross-linking agent added is small, the effect of cross-linking cannot be obtained, and if it is large, the heating return becomes too large. The addition amount of the cross-linking agent is restricted by the value of the intrinsic viscosity [η], and the addition amount is determined by measuring the [η] of the resin sheet when no cross-linking agent is added, and using the value, the formula (1) is used. And within the range calculated from (2) (hatched in Fig. 1).

Intrinsic viscosity [η] When the intrinsic viscosity [η] is high, the solvent resistance is improved, but when compared with the case where the intrinsic viscosity [η] is low, molding in a region where the ratio of rubber elastic state is high is Therefore, the heating return becomes large.
On the other hand, if it is low, the solvent resistance deteriorates. The solvent resistance and heating return due to this [η] depend on the addition amount of the cross-linking agent. Therefore, considering the addition amount of the cross-linking agent, within the range calculated from the formulas (1) and (2) (see FIG. 1). (Within the diagonal line).

The acrylic product produced by the above method has a small amount of heat return. Specifically, in the evaluation of the heating reversion property shown below, a value of 5.0 or less is obtained. If it exceeds 5.0, the occurrence rate of defects such as peeling and spread of scratches becomes extremely large by the hot water resistance test exceeding 80 ° C. Therefore, in consideration of solvent resistance and moldability, it is possible to obtain an acrylic resin product that is less likely to cause product defects such as scratch expansion due to heating return.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. The evaluation in the examples was carried out by the following method.

Example 1 To 100 kg of methyl methacrylate, 60 g of 2,2'-azobis (2,4-dimethylvaleronitrile) (hereinafter abbreviated as "CN") was added and placed in a tank-type polymerization reactor, It was heated at 90 ° C or higher for 13 minutes and cooled to room temperature to obtain a syrup containing 22% of the polymer.

Next, 4 g of CN, 6 g of n-dodecyl mercaptan (hereinafter abbreviated as "nDM") and 15 g of ethylene glycol dimethacrylate (hereinafter abbreviated as "EDMA") were added to 10 kg of this syrup to remove bubbles, and then strengthened. It was poured into a mold composed of glass and a soft vinyl chloride gasket and heated at 74 ° C. for 35 minutes and then at 125 ° C. for 90 minutes to obtain a sheet having a plate thickness of 5 mm. Under this polymerization condition, ED was added to the syrup.
The [η] of the sheet obtained when MA was not added was 0.11.
(l / g).

Then, this sheet was annealed at 78 ° C. for 3 hours.
And gradually cooled at 15 ° C./hour.

The sheet thus obtained (270 × 270
(mm, thickness 5 mm) both sides are heated to 180 ° C with an infrared heater, and then vacuum-molded using a cylindrical mold with a diameter of 220 mm and a height of 140 mm to obtain a bend radius Rmm of the corner of the molded product. I asked.

Next, a 0.8 mm thick plate was cut out from the vacuum-formed product, and one surface was reinforced with a reinforced resin material.
First, as a primer treatment, a commercially available vinyl ester resin
A mixture of 1.5 parts of a curing agent and 0.5 part of an accelerator was applied to 100 parts, dried, and then three commercially available chopped strand glass mats were laminated. Further, a mixture of 100 parts of a commercially available unsaturated polyester resin and 1 part of a curing agent was applied and impregnated.

A V-shaped scratch with a depth of 0.1 mm was formed on the surface of the reinforced molded sample on the acrylic resin side at a temperature of 97 mm.
The sample was exposed to an environment of ° C and 100% relative humidity for 3 hours, and the extent of scratches was observed with an optical microscope to determine the amount of change from the initial value (1.0 times when there was no change). Table 1 shows the obtained results.

Example 2 3 g of nDM and 10 g of EDMA were added to 10 kg of syrup.
A sheet having a plate thickness of 5 mm was obtained and reinforced under the same conditions as in Example 1 except that g was used. [Η] of the sheet obtained when EDMA was not added to the syrup under these polymerization conditions
Was 0.17 (l / g).

Example 3 A sheet having a thickness of 5 mm was obtained and reinforced under the same conditions as in Example 1 except that EDMA added to 10 kg of syrup was changed to 15 g. The [η] of the sheet obtained when EDMA was not added to the syrup under these polymerization conditions was 0.11 (l / g).

Example 4 To a monomer mixture consisting of 96 kg of methyl methacrylate and 4 kg of n-butyl acrylate, 100 g of CN and 65 g of nDM were added and placed in a tank-type polymerization reactor at 90 ° C. or higher. Heat for 17 minutes,
Cooling to room temperature gave a syrup containing 27% polymer.

Next, 4 g of CN and EGD were added to 10 kg of this syrup.
After defoaming by adding 15 g of M, the thickness is 5 mm in the same manner as in Example 1.
Sheet was obtained and reinforced. The [η] of the sheet obtained when EGDM was not added to the syrup under these polymerization conditions was 0.10 (l / g).

Comparative Example 1 A syrup was obtained in the same manner as in Example 1. Then this syrup 10k
After defoaming by adding 4 g of CN to g, a sheet having a plate thickness of 5 mm was obtained and reinforced in the same manner as in Example 1. The [η] of this sheet was 0.23 (l / g).

Comparative Example 2 To 100 kg of methyl methacrylate, 5 g of 2,2'-azobis (isobutyronitrile) was added and placed in a tank type polymerization reactor.
It was heated at 0 ° C or higher for 20 minutes and cooled to room temperature to obtain a syrup containing 13% of the polymer.

Next, 1.5 g of 2,2'-azobis (isobutyronitrile) was added to a mixture of 9.5 kg of this syrup and 0.5 kg of methyl acrylate to remove bubbles, and then tempered glass and soft vinyl chloride were added. It was poured into a mold composed of a gasket made of a material and heated at 65 ° C. for 90 minutes and then at 125 ° C. for 90 minutes to obtain a sheet having a plate thickness of 5 mm. It was reinforced in the same manner as in Example 1. The [η] of this sheet was 0.50 (l / g).

[0046]

[Table 1]

[0047]

EFFECTS OF THE INVENTION The acrylic product obtained by the production method of the present invention is excellent in hot water resistance and is less likely to cause product defects such as expansion of scratches due to heating back, and has excellent performance especially as an acrylic bath.

[Brief description of the drawings]

FIG. 1 is a diagram showing a range of [η] value and a cross-linking agent addition amount corresponding to a region of a small return of heating of the present invention.

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Claims (1)

[Claims] 1. A syrup obtained by adding a polymerization initiator and a chain transfer agent to a monomer mixture of methyl methacrylate alone or a monomer mixture of 94% by weight or more of methyl methacrylate and 6% by weight or less of an acrylic acid ester to partially polymerize the syrup. And then thermoforming an acrylic resin sheet obtained by cast polymerization in which a crosslinking agent and a polymerization initiator are added to the obtained syrup to perform heat treatment, and an acrylic resin reinforced with a reinforced resin material is produced. In the method of obtaining a product, in the process of cast polymerization performed by adding a crosslinking agent and a polymerization initiator to the syrup and performing heat treatment, [η] of the sheet completely polymerized in the absence of the crosslinking agent is A ( l / g) (1) When 0.05 ≤ A <0.10 0.5-4 × A ≤ B ≤ 0.9-4 × A (1) (2) When 0.10 ≤ A ≤ 0.20 0.02 ≤ B ≤ 0.9-4 x A ... Equations (1) and (2) represented by (2) B to be limited in scope
Use the acrylic resin sheet obtained by the formula in which the value of is the addition amount (% by weight) of the cross-linking agent.
Thermoforming in the temperature range of 0 to 200 ° C, then holding at a temperature of 75 to 80 ° C for 1.5 hours or more and then 15 ° C per hour
A method for producing an acrylic product, characterized in that molding strain during thermoforming is removed by slow cooling at the following cooling rate, and then reinforcement is performed with a reinforcing resin material.