JP2004176043A - Manufacturing method of acrylic syrup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide acrylic syrup which produces a cured product substantially having no outward-appearance defect such as foaming even when cured in a short time and which is excellent in handling properties. <P>SOLUTION: The manufacturing method of acrylic syrup comprises a step for polymerizing a feed material which includes methyl methacrylate, and has a carboxylic acid content of 0.04 mmol/L or less and a water content of 15 mmol/L or less, to a polymerization degree of ranging 1-50 mass% in the presence of a radical polymerization initiator, wherein it is preferred that the carboxylic acid content is 0.02 mmol/L or less and the water content is 10 mmol/L or less. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a method for producing an acrylic syrup containing methyl methacrylate, which hardly foams during curing.

  Conventionally, acrylic syrup has been used as an intermediate material for, for example, methacrylic resin casting plates, optical materials such as optical fibers, artificial marble, flooring materials, and adhesives. With respect to a method for producing an acrylic syrup containing methyl methacrylate as a main component, for example, a chain transfer agent having a boiling point of 100 ° C. or less is added to methyl methacrylate, and a part of the chain transfer agent is polymerized. There is disclosed a method for producing a syrup capable of producing a high-quality syrup and shortening the production time of a casting plate (for example, see Patent Document 1).

As a method of improving the production efficiency of the cured product or shortening the operation time when curing the acrylic syrup, there is a method of increasing the amount of the polymerization initiator to be added. However, this method has a drawback that it is difficult to control the curing and foaming is likely to occur in the cured product. In addition, when the amount of the polymerization initiator added is reduced to avoid foaming, the time until the completion of curing becomes longer and the working efficiency is reduced. Further, when the polymerization rate of the syrup is increased in order to shorten the curing time, there is a problem that the syrup has a low viscosity because the viscosity of the syrup increases.
JP-A-50-35277

  An object of the present invention is to solve the above-mentioned problems of the related art. That is, an object of the present invention is to provide an acrylic syrup that has substantially no appearance defects such as foaming in a product after syrup curing even when cured in a short time, and has excellent handleability.

  The present inventors have conducted intensive studies to achieve the above object, and as a result, an acrylic syrup produced from a specific raw material containing methyl methacrylate is less likely to have appearance defects such as foaming during further curing, and has a poor handling property. The inventors have found that excellent effects can be obtained in which the optical properties and mechanical properties of the cured acrylic syrup product are not impaired, and have completed the present invention.

  That is, the present invention relates to a method for preparing a raw material containing methyl methacrylate, which has a carboxylic acid compound content of 0.04 mmol / L or less and a water content of 15 mmol / L or less, in the presence of a radical polymerization initiator. This is a method for producing an acrylic syrup having a step of polymerizing to a range of 1 to 50% by mass.

  ADVANTAGE OF THE INVENTION According to this invention, even if it cure | hardens in a short time, the syrup which has substantially no appearance defect, such as foaming, in a product after syrup hardening and which was excellent in handleability can be manufactured.

  The raw material used in the present invention contains methyl methacrylate (hereinafter, referred to as “MMA”). The raw material may be a raw material composed of MMA alone. Further, a raw material comprising a mixture of MMA of 50% by mass or more and another copolymerizable monomer may be used.

  Other monomers copolymerizable with MMA are not particularly limited. Specific examples thereof include ethyl methacrylate, isopropyl methacrylate, t-butyl methacrylate, s-butyl methacrylate, n-butyl methacrylate, amyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, Methacrylates other than MMA, such as phenyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, benzyl methacrylate, isobornyl methacrylate, 1-menthyl methacrylate, adamantyl methacrylate, and dimethyl adamantyl methacrylate; methyl acrylate, acrylic acid Ethyl, isopropyl acrylate, butyl acrylate, t-butyl acrylate, amyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, Acrylic esters such as cyclohexyl acrylate, phenyl acrylate, and benzyl acrylate; vinyl aromatics such as styrene, α-methylstyrene, paramethylstyrene, isopropenylstyrene, and vinyltoluene; non-acrylic esters such as acrylonitrile and methacrylonitrile Saturated nitriles; polyunsaturated compounds such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and divinylbenzene. In addition, one of these copolymer components may be used alone for MMA, or two or more of them may be used in combination for MMA as needed.

  The composition of the raw material is preferably 50 to 100% by mass of MMA and 50 to 0% by mass of another monomer copolymerizable with MMA. In particular, from the viewpoint of not impairing the physical properties of acrylic syrup, it is more preferable that the amount of MMA is 90% by mass or more and the amount of other copolymerizable monomer is 10% by mass or less.

  In the present invention, the raw material used has a carboxylic acid compound content of 0.04 mmol / L or less and a water content of 15 mmol / L or less in order to make foaming less likely to occur during curing of the acrylic syrup.

  Examples of the carboxylic acid compound contained in the raw material used in the present invention include formic acid, acetic acid, acrylic acid, propionic acid, methacrylic acid and the like.

  In the present invention, examples of the method for reducing the content of the carboxylic acid compound in the raw material to a certain amount or less include washing with water, neutralization with an alkali, adsorption with an anionic ion exchange resin, and distillation using a difference in boiling point.

  Methods for reducing the water content in the raw material to a certain level or less include azeotropic distillation with the addition of an azeotropic solvent, treatment with an adsorbent, and the like.

  The carboxylic acid compound content is preferably 0.02 mmol / L or less, and more preferably lower.

  The water content is preferably 10 mmol / L or less, and more preferably lower.

  In the present invention, a raw material containing MMA, having a carboxylic acid compound content of 0.04 mmol / L or less and a water content of 15 mmol / L or less is partially prepared in the presence of a radical polymerization initiator. Polymerize. The radical polymerization initiator used is not particularly limited. Specific examples include 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, and 2,2′-azobis- (2,4-dimethyl Azo-based polymerization initiators such as valeronitrile); lauroyl peroxide, diisopropylperoxydicarbonate, benzoyl peroxide, bis (4-t-butylcyclohexyl) peroxydicarbonate, t-butylperoxyneodecanoate, t And organic peroxide-based polymerization initiators such as hexyl peroxypivalate. These can be used alone or in combination of two or more as needed. The addition amount of the radical polymerization initiator is preferably about 0.01 to 0.5 part by mass with respect to 100 parts by mass of the raw material.

  When polymerizing the raw materials, the polymerization may be performed by adding a chain transfer agent such as mercaptan.

  When a part of the carboxylic acid compound and the water contained therein are polymerized using a raw material having a certain amount or less, the polymerization is carried out up to a polymerization rate of 1 to 50% by mass. When the polymerization rate is 1% by mass or more, the curing time at the time of curing the acrylic syrup is shortened, and appearance defects are less likely to occur. In addition, when the polymerization rate is 50% by mass or less, the viscosity of the syrup decreases, and the handleability of the syrup improves. In order to shorten the curing time during syrup curing and to reduce appearance defects, the higher the polymerization rate, the better. However, in consideration of the handling properties of the syrup and the mixing properties of the additives, it is particularly preferable that the polymerization rate is in the range of 5 to 40% by mass.

  The method of polymerizing a part of this raw material is not particularly limited, and various methods known in the art can be used as long as the method can polymerize a raw material having a carboxylic acid compound and water having a certain amount or less to a polymerization rate of 1 to 50% by mass. A polymerization method can be used. For example, there is a method in which a part of the raw material is subjected to bulk polymerization in a reactor. The reactor includes, for example, a reactor provided with a cooler inside or at the top. Further, it is preferable that the inside of the reactor is at atmospheric pressure and the oxygen concentration is reduced by an inert gas such as nitrogen gas. The temperature at the time of the polymerization is preferably set to a temperature within a range from a temperature about 10 ° C. lower than the boiling point of the raw material to the boiling point of the raw material, and particularly preferably a temperature near the boiling point of the raw material.

  After a part of the raw material is polymerized into acrylic syrup, it is preferable to add a polymerization inhibitor in order to avoid coloring and natural curing of the acrylic syrup. Specific examples of the polymerization inhibitor include hydroquinone, hydroquinone monomethyl ether, 2,6-di-t-butyl-4-methylphenol, and 2,4-dimethyl-6-t-butylphenol. These can be used alone or in combination of two or more as needed.

  Further, in the present invention, if necessary, various conventionally known additives such as stabilizers such as antioxidants and ultraviolet absorbers; flame retardants; dyes and pigments used for coloring; Can be added to the raw material before partially polymerizing or the syrup after partially polymerizing.

  The acrylic syrup obtained by the present invention can be used for various conventionally known applications. For example, a polymerization initiator can be added to the acrylic syrup and cured in a mold to obtain a desired molded product, or can be cured in a void to obtain a desired reinforcing / filling material. The acrylic syrup obtained according to the present invention is excellent in workability in such use, hardly causes appearance defects such as foaming in the cured product, and further has excellent optical properties unique to the cured acrylic syrup. And the mechanical properties are not impaired.

  Hereinafter, the present invention will be described in more detail with reference to examples. In the following description, “parts” and “%” representing the quantitative ratios are based on mass unless otherwise specified. Evaluation of various physical properties and adjustment of raw materials used were carried out by the following methods.

(1) Carboxylic acid compound amount The amount of the carboxylic acid compound in the raw materials used was measured by a neutralization titration method.

(2) Water Content The water content in the raw materials used was measured by Karl Fischer titration in accordance with JIS K0113 and K0068.

(3) Polymerization rate The sample was put into a large amount of hexane, the resulting precipitate was filtered, the residue was dried under reduced pressure, the mass was measured, and the ratio to the mass of the original sample measured in advance was calculated. The value was taken as the conversion.

(4) Viscosity The viscosity at 20 ° C. was determined using a B-type viscometer.

(5) Appearance After the syrup was cured, the product was visually observed for surface defects, internal foaming and the like.

(6) Adjustment of Raw Materials Used As raw materials, MMA alone having a carboxylic acid compound content of 0.13 mmol / L and a water content of 35 mmol / L, or, if necessary, MMA and another copolymerizable monomer Was used. When lowering the carboxylic acid compound content, MMA alone or a mixture is brought into contact with an anionic ion exchange resin, and the space velocity is increased or decreased, so that the carboxylic acid compound content in the MMA alone or the mixture before the contact is reduced. Raw materials of various contents were obtained. When lowering the water content, the MMA alone or mixture is brought into contact with molecular sieves to increase or decrease its space velocity so that various contents lower than the water content in the MMA alone or mixture before the contact are obtained. Raw material was obtained.

[Example 1]
To a polymerization vessel equipped with a cooling pipe, a thermometer, and a stirrer, supply 100 parts of MMA containing 0.02 mmol / L of a carboxylic acid compound and 5 mmol / L of water, and stir at -90 kPa (gauge pressure). The pressure was reduced for 10 minutes. Then, the pressure was returned to the atmospheric pressure with nitrogen gas, heating was started, and when the internal temperature reached 60 ° C., 2,2′-azobis- (2,4-dimethylvaleronitrile), which was a radical polymerization initiator, was added. Then, the mixture was heated to an internal temperature of 100 ° C. and maintained for 8 minutes. Thereafter, the mixture was cooled to room temperature by cooling under reduced pressure, and 0.002 parts of 2,4-dimethyl-6-t-butylphenol as a polymerization inhibitor was added to obtain an acrylic syrup. The polymerization rate of this acrylic syrup was about 20%, and the viscosity was 1.5 Pa · s.

  To 100 parts of this acrylic syrup, 0.2 part of t-hexyl peroxypivalate as a radical polymerization initiator was added, stirred, and degassed at -90 kPa (gauge pressure) for 5 minutes. This acrylic syrup was injected into a mold, which is two tempered glass plates of 300 × 300 × 6 mm laminated at intervals of about 8 mm via a polyvinyl chloride gasket and fixed by a clamp. Then, the mold into which the syrup was injected was immersed in warm water at 78 ° C. for 20 minutes to polymerize and cure, and then heat-treated in an air heating furnace at 130 ° C. for 40 minutes, cooled to 90 ° C., and then cured in the mold. The product was peeled off to obtain a methacrylic resin casting plate having a plate thickness of about 6 mm. Table 1 shows the results of observing the appearance of this methacrylic resin casting plate.

[Example 2]
In a polymerization vessel similar to that of Example 1, a raw material consisting of 95 parts of MMA and 5 parts of butyl acrylate (hereinafter referred to as “BA”) was contained, in which the carboxylic acid compound contained was 0.01 mmol / L and the water content was 14 mmol / L. The raw material as L was supplied, and 0.06 parts of n-dodecyl mercaptan was further added as a chain transfer agent, and the pressure was reduced at -90 kPa (gauge pressure) for 10 minutes with stirring. Next, the pressure was returned to the atmospheric pressure with nitrogen gas, heating was started, and when the internal temperature reached 80 ° C., 2,2′-azobis- (2,4-dimethylvaleronitrile), which was a radical polymerization initiator, was increased to 0.1%. 08 parts was added, and the mixture was further heated to an internal temperature of 100 ° C. and maintained for 10 minutes. Thereafter, the mixture was cooled to 15 ° C. by cooling under reduced pressure, and 0.0005 parts of 2,6-di-t-butyl-4-methylphenol as a polymerization inhibitor was added to obtain an acrylic syrup. The polymerization rate of this acrylic syrup was about 26%, and the viscosity was 1.7 Pa · s. To 100 parts of this acrylic syrup, 0.15 parts of 2,2'-azobisisobutyronitrile as a radical polymerization initiator was added, stirred, and degassed under reduced pressure at -90 kPa (gauge pressure) for 10 minutes. This acrylic syrup is formed of two transparent methacrylic resin plates having a size of 500 × 500 mm × 6 mm laminated at intervals of about 4 mm via a polyvinyl chloride gasket, and is fixed to a mold (adhesive layer cell). ). Next, the mold into which the syrup was poured was placed in an air heating furnace, and polymerized and cured at 55 ° C. for 5 hours. An adhesive plate was obtained. Table 1 shows the results of observation of the appearance of the resin adhesive plate.

[Comparative Example 1]
An acrylic syrup was prepared in the same manner as in Example 1 except that the carboxylic acid compound contained in the MMA used was 0.06 mmol / L and the water content was 22 mmol / L, to obtain a methacrylic resin casting plate. Table 1 shows the appearance observation results.

[Comparative Example 2]
An acrylic syrup was prepared in the same manner as in Example 2 except that the carboxylic acid compound contained in the raw material composed of MMA and BA used was 0.12 mmol / L and the water content was 13 mmol / L, and a resin adhesive plate was prepared. Got. Table 1 shows the appearance observation results.

表１に示すように、実施例１および２では、含有するカルボン酸化合物および水分が一定量以下のＭＭＡ単独またはＭＭＡとＢＡとからなる原料を使用したので、良好な外観の硬化製品を短時間で得ることができた。一方、比較例１、２および３では、含有するカルボン酸化合物または水分が一定量を超えたＭＭＡ単独またはＭＭＡとＢＡとからなる原料を用いたので、微小な発泡が多数発生し、硬化製品の外観が劣っていた。 [Comparative Example 3]
An acrylic syrup was prepared in the same manner as in Example 2 except that the carboxylic acid compound contained in the raw material composed of MMA and BA used was 0.03 mmol / L and the water content was 33 mmol / L, and a resin adhesive plate was prepared. Got. Table 1 shows the appearance observation results.

As shown in Table 1, in Examples 1 and 2, a carboxylic acid compound and a raw material composed of MMA and BA containing only a certain amount of water or less were used. Was able to get in. On the other hand, in Comparative Examples 1, 2 and 3, since a carboxylic acid compound or a raw material composed of MMA alone or MMA containing BA exceeding a certain amount was used, a large number of fine foams were generated, and a cured product was obtained. The appearance was poor.

  As described above, according to the present invention, even when cured in a short time, there is substantially no appearance defect such as foaming in a product after syrup curing, and it is possible to produce an acrylic syrup excellent in handleability. Since it can be used, it is useful as an intermediate material for optical materials such as methacrylic resin casting plates and optical fibers, artificial marble, flooring materials and adhesives.

Claims (1)

  A raw material containing methyl methacrylate, having a carboxylic acid compound content of 0.04 mmol / L or less and a water content of 15 mmol / L or less, is subjected to a polymerization rate of 1 to 50% by mass in the presence of a radical polymerization initiator. A method for producing an acrylic syrup, comprising the step of polymerizing to the range of.