JP6164794B2 - Acrylic polymer and method for producing the same - Google Patents

Description

  The present invention relates to an acrylic polymer and a method for producing the same.

  Methacrylic resins have excellent optical properties, weather resistance, and high mechanical properties, and are therefore widely used in automotive parts, lighting equipment, OA equipment parts, and the like. Furthermore, in recent years, with the development of LED light sources, they are widely used in optical applications such as light guide plates for thin TV front panels.

  The methacrylic resin product used for the various uses described above is obtained by using, for example, a cast product of methacrylic resin, a molded product by extrusion molding, injection molding, or the like.

  In the above-described extrusion molding and injection molding, it is usually produced at a molding temperature of 200 to 280 ° C.

  Further, in recent years, since optical components have been increased in size, there are increasing opportunities to be produced by an injection molding method or an extrusion molding method as a method for manufacturing optical components. Further, in order to shorten the molding cycle and increase the productivity, the molding temperature tends to be increased to improve the fluidity of the resin.

  Thus, in recent years, methacrylic resins used for obtaining optical components have a high tendency to receive a lot of thermal history.

  On the other hand, as a method for producing methyl methacrylate which is one of monomer raw materials for obtaining a methacrylic resin, an ACH method with by-product of ammonium sulfate, an improved ACH method without by-product of ammonium sulfate, and a C2 component Alternatively, various industrial production methods such as an oxidation method of C4 component and a method of obtaining methyl methacrylate directly from methacrolein and methanol can be mentioned, but in recent years, oxidation of C2 component or C4 component is more than the ACH method using sulfuric acid. The law has been used a lot.

  The type and content of impurities contained in methyl methacrylate vary depending on the production method, but the presence of impurities contained in methyl methacrylate has been a problem until now, especially when using methacrylic resin products for optical member applications. Even a very small amount of impurities that have not been observed may cause problems due to decomposition of impurities or coloring due to side reactions during polymerization or molding.

  In particular, when a methacrylic resin is produced by continuous bulk polymerization or continuous solution polymerization, the process for removing unreacted monomers and solvents when recovering the obtained polymer is subject to a lot of heat history. Coloring becomes more prominent than in the case of production by cast polymerization.

  In such a situation, for example, Patent Document 1 discloses purification for obtaining a (meth) acrylic acid ester having a low content of 2,5-dimethylfuran, which is an impurity generated in the above-described method for producing methyl methacrylate. A method has been proposed.

JP 2001-122826 A

  However, although the (meth) acrylic acid ester obtained in Patent Document 1 is effective in the production of methacrylic resin products by cast polymerization, methacrylic acid obtained by a method that receives more heat history such as continuous bulk polymerization or continuous solution polymerization. This is not sufficient in the manufacture of resin-based resin products.

  The present invention provides an acrylic polymer that exhibits good moldability even under harsh polymerization conditions or molding conditions that achieve high productivity, and that can provide molded products with excellent coloration resistance and thermal stability. The purpose is to do.

The gist of the present invention is that a monomer raw material is passed through a weakly basic anion exchange resin and then a partial polymerization solution obtained by continuous partial polymerization is supplied to a devolatilizing extruder to perform polymerization. An acrylic polymer having a 2,5-dimethylfuran concentration of 0.2 ppm or less and an organic acid concentration converted to methacrylic acid of 1 ppm or less (hereinafter referred to as “the present polymer”). "). Here, “partial polymerization” refers to polymerization of a part of the monomer raw material.

  This polymer exhibits good moldability even under harsh polymerization conditions or molding conditions that realize high productivity such as a method of receiving more thermal history such as continuous bulk polymerization and continuous solution polymerization, coloring resistance and Because it is possible to obtain molded products with excellent thermal stability, automotive parts, lighting equipment, OA equipment parts, various light guides, video lenses, optical disks, optical fibers, LCD monitor screens, computer screens, and various types It is suitable for various uses such as optical components such as a light guide plate for a TV front panel.

Furan ring structure

In the present invention, the furan ring structure is one of impurities contained in the polymer, and may be contained in the polymer at 0.2 ppm or less.

  A furan ring structure is one of the compounds produced as a by-product when producing a monomer for obtaining the present polymer (hereinafter referred to as “the present monomer”) or for producing the present polymer. It is.

Examples of the furan ring structure include furan, 2-methylfuran, 3-methylfuran, furfuran, 2,3-dihydro-4-methylfuran, and 2,5-dimethylfuran. These may be included in the polymer alone or in the form of a mixture. In the present invention, the concentration of 2,5-dimethylfuran in the polymer is 0.2 ppm or less .

Organic acid
In the present invention, the organic acid is one of the impurities contained in the polymer, and is contained in the polymer at a concentration of 1 ppm or less when converted to methacrylic acid.
In the present invention, the concentration of the organic acid in the polymer refers to the concentration when converted to the concentration of methacrylic acid.

  An organic acid is one of the compounds produced as a by-product during the production of the present monomer or the present polymer.

Examples of the organic acid include methacrylic acid, formic acid, acetic acid, and propionic acid .

This polymer
This polymer contains 2,5-dimethylfuran of 0.2 ppm or less and an organic acid having a concentration of 1 ppm or less in terms of methacrylic acid .
As this polymer, the homopolymer of alkyl methacrylate and the copolymer of alkyl methacrylate and alkyl acrylate are mentioned, for example.

  Examples of the alkyl methacrylate include methyl methacrylate.

  Examples of the alkyl acrylate used as a raw material for obtaining a copolymer of alkyl methacrylate and alkyl acrylate include alkyl acrylates having 1 to 8 carbon atoms.

  Specific examples of the alkyl acrylate having 1 to 8 carbon atoms include methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, acrylic acid Examples include t-butyl and 2-ethylhexyl acrylate. These can be used alone or in combination of two or more. Of these, methyl acrylate, ethyl acrylate and n-butyl acrylate are preferred.

  In the present invention, as the present polymer, from the viewpoint of heat resistance, chemical resistance and fluidity of the present polymer, 90 to 100% by mass of methyl methacrylate units and 0 to 0 alkyl acrylate units having 1 to 8 carbon atoms. A polymer containing 10% by weight is preferred.

  A known radical polymerization method may be mentioned as a method for producing the present polymer.

  When the present polymer is produced by radical polymerization, a polymerization initiator or a chain transfer agent can be contained in the present monomer.

  As a polymerization initiator, the catalyst and radical polymerization initiator which consist of metal complexes are mentioned, for example.

  Among the above compounds, a radical polymerization initiator is preferred from the viewpoint of preventing coloring due to the remaining metal atoms in the polymer.

  Specific examples of the radical polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), dimethyl 2,2′-azobisisobutyrate and the like. Azo compounds; and organic compounds such as tert-butyl peroxylaurate, tert-butyl peroxyisobutyrate, tert-butyl peroxy 2-ethyl hexanate, tert-butyl peroxy-3,5,5-trimethyl hexanate A peroxide is mentioned.

  Examples of the chain transfer agent include alkyl mercaptans.

  Specific examples of the alkyl mercaptan include n-propyl mercaptan, isobutyl mercaptan, n-butyl mercaptan, n-hexyl mercaptan, n-heptyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan and tert-dodecyl mercaptan.

  In the present invention, the alkyl mercaptan is preferably an alkyl mercaptan having 3 to 9 carbon atoms in terms of devolatilization and odor, and more preferably n-butyl mercaptan and n-octyl mercaptan in terms of devolatilization and price. preferable.

  As content of the chain transfer agent in this monomer, 0.05-1.0 mass part is preferable with respect to 100 mass parts of this monomer.

  When the content of the chain transfer agent is 0.05 parts by mass or more, preferably 0.1 parts by mass or more, the polymer tends to have an appropriate molecular weight that can be used as a molding material. . In addition, the content of the chain transfer agent is 1.0 part by mass or less, preferably 0.5 part by mass or less, thereby improving the thermal decomposition resistance of the polymer due to an increase in the amount of sulfur-terminated terminals and the present polymer. The total amount of sulfur-based compounds therein is suppressed, and a decrease in molecular weight of the present polymer is suppressed, and good strength tends to be maintained.

  When obtaining this polymer using a radical polymerization initiator and a chain transfer agent, it is preferable to adjust the amounts used of the radical polymerization initiator and the chain transfer agent and to control the polymerization temperature and the polymerization time.

  As said conditions, the conditions which reduce the amount of initiators, increase a chain transfer agent, and superpose | polymerize at about 100-150 degreeC for 1 to 3 hours are preferable.

  In the present invention, specific examples of the method for producing the present polymer by the radical polymerization method include a continuous bulk polymerization method, a continuous solution polymerization method and a bag polymerization method.

  In the case of obtaining the present polymer by a continuous solution polymerization method, examples of a method for recovering the present polymer from the obtained polymerization solution include a solvent reprecipitation method.

  Specific examples of the method for recovering the present polymer by the solvent reprecipitation method include a method in which the polymer solution is added to a poor solvent such as methanol and hexane, reprecipitated and recovered, and then dried.

  A specific example of the method for recovering the present polymer by the continuous bulk polymerization method is a method of pelletizing and recovering the liquid material after the bulk polymerization.

  Among the above methods, the continuous bulk polymerization method described in, for example, JP-A-58-88701 and JP-A-2000-26507 is disclosed in terms of thermal decomposition resistance, production operability and productivity of the present polymer. The production method is preferred.

  As a specific example of the production method of the present polymer by the continuous bulk polymerization method, a partial polymerization solution obtained by continuously partial polymerization of a monomer raw material for obtaining an acrylic polymer is supplied to a devolatilizing extruder. There is a method in which the polymerization is completed and volatiles are separated and removed by devolatilization.

  Examples of the devolatilization method in the production method of the present polymer by the continuous bulk polymerization method include a thin film devolatilization method and a devolatilization method using a devolatilization extruder. Among these, a devolatilization method using a devolatilization extruder is preferable from the viewpoint of heat history and productivity of the polymer.

  In the present invention, in order to use the present monomer efficiently, a volatile-containing recovered material collected by separating and removing volatile materials can be charged as a recycled material into the monomer material.

  In the present invention, the polymer may contain various additives such as a mold release agent, an antioxidant, an ultraviolet absorber, and a dye / pigment, if necessary.

Examples of the method of adding the additive include a method of dissolving in a monomer raw material and a method of blending with the present polymer before pelletizing the present polymer.

Monomer raw material

In the present invention, the monomer raw material contains the monomer and, if necessary, a polymerization initiator and a chain transfer agent.

  In the present invention, for example, when a monomer raw material containing methyl methacrylate is polymerized by a continuous polymerization method such as a continuous bulk polymerization method, it is contained in methyl methacrylate used as the monomer. The concentration of 5-dimethylfuran is preferably 30 ppm or less.

In addition, when polymerizing a monomer raw material containing methyl methacrylate by the continuous bulk polymerization method, formic acid and formaldehyde are generated by air oxidation, so this monomer is deoxygenated by nitrogen substitution etc. Is preferably used. Moreover, as polymerization temperature in this method, 100-180 degreeC is preferable.

Partial polymerization solution

In the present invention, the partial polymerization solution is a syrup-like product in which the present polymer is dissolved in a monomer raw material for obtaining the present polymer.

The polymerization rate of the partial polymerization solution is preferably 40 to 70% in terms of devolatilization efficiency and production efficiency.

Devolatilizing extruder

As a devolatilization extruder used by this invention, the screw type extruder which has the vent part for devolatilization is mentioned, for example.

  The temperature of the devolatilization part in the devolatilization extruder is preferably equal to or higher than the polymerization temperature.

  In addition, a devolatilization part is located upstream of a devolatilization extruder, and points out the part for isolate | separating this polymer efficiently from the syrup-like thing which is a partial polymerization solution.

  In this invention, 190-300 degreeC is preferable as a temperature of the devolatilization part in a devolatilization extruder, and 190-260 degreeC is more preferable. By setting the temperature of the devolatilization part to 190 ° C. or higher, the fluidity of the partial polymer solution capable of performing efficient devolatilization tends to be obtained. Moreover, it exists in the tendency which can maintain the viscosity of the partial polymer solution which can suppress decomposition | disassembly of this polymer and can implement efficient devolatilization by setting the temperature of a devolatilization part to 300 degrees C or less.

In this invention, 1.3-11 kPa (10-80 torr) is preferable as a pressure reduction degree of the devolatilization part in a devolatilization extruder. By setting the degree of vacuum in the devolatilization part to 1.3 kPa (10 torr) or more, the removal rate of impurities in the polymer tends to be good .

Volatile collection
In the present invention, the volatile matter-containing recovered product is a volatile substance in the partially polymerized solution when the partial polymerization solution obtained by continuously partially polymerizing the monomer raw material is supplied to the devolatilizing extruder to complete the polymerization. The components are separated and removed and collected outside the devolatilizing extruder.
When the volatile-containing recovered product is charged into the monomer raw material as a recycled raw material, for example, in order to reduce the concentration of furan ring structure and organic acid in the obtained polymer, an adsorbing resin, It is preferable to treat with an ion exchange resin or an amine component.

  When continuous production of the present polymer is performed, the recovered volatile-containing recovered material is temporarily stored in a storage tank and used by mixing with the monomer not including the recovered material. In the case of producing the present polymer by the continuous polymerization method, the volatile matter-containing recovered product is used in a devolatilizing extruder from the continuous bulk polymerization vessel in which the amount of liquid corresponding to the full liquid recovered in the storage tank is The case where all the steps up to the devolatilization section are passed is defined as one time. When performing continuous production of this polymer, the ratio of the unreacted main monomer in the recovered product and the newly added monomer not including the recovered material, and the number of times of use are It adjusts by the heat history etc. in the polymerization reactor or devolatilization extruder of a polymer raw material. The content of the recovered product in the raw material monomer is preferably in the range of 10 to 40% by mass.

In the case of carrying out production by continuous bulk polymerization using the volatile-containing recovered material collected by separating and removing the above volatiles, in terms of suppressing the yellowish color of the molded product using this polymer, The concentration of 2,5-dimethylfuran in the monomer raw material (ppm × 10 ⁻⁶ ), the absolute temperature (K) of the devolatilization part in the extruder, and the multiplier of each numerical value of the continuous polymerization period (days) (hereinafter, “ The "continuous operation multiplier" is preferably 2 or less, more preferably 1 or less. That is, the continuous operation multiplier should be 2 or less by reducing at least one of the concentration of 2,5-dimethylfuran in the monomer raw material, the absolute temperature of the devolatilization part in the extruder, and the continuous polymerization period. Therefore, yellowish color can be suppressed.

Hereinafter, the present invention will be described by way of examples. In the examples and comparative examples, “parts” and “%” indicate “parts by mass” and “mass%”, respectively. Further, the concentration of 2,5-dimethylfuran and the concentration of organic acid in the monomer or acrylic polymer in the following Examples and Comparative Examples, and the yellowness (YI value) of the molded product obtained using this polymer ) Was evaluated by the following method.
(1) Concentration of 2,5-dimethylfuran Using a solution obtained by dissolving a certain amount of monomer or acrylic polymer pellets in acetone as a sample, the concentration of 2,5-dimethylfuran was measured by Gas from Agilent Technologies. It measured using the chromatography mass spectrometer (brand name: HP-6890 / HP-5993).

In the measurement, the concentration of 2,5-dimethylfuran was determined using a calibration curve prepared in advance based on the strength of 2,5-dimethylfuran relative to the strength of the internal standard substance.
(2) Concentration of organic acid A solution obtained by dissolving a certain amount of monomer or acrylic polymer pellets in acetone and then adding a small amount of methanol was used as a sample, and an automatic titrator manufactured by Hiranuma Sangyo Co., Ltd. (trade name: COM550) The concentration of organic acid as methacrylic acid was determined by neutralization titration in a nitrogen atmosphere.
(3) YI value Using a Toshiba Co., Ltd. injection molding machine (trade name: IS80FPA3), a 200 mm x 30 mm x 10 mm mold was attached, the cylinder temperature was 250 ° C, the mold temperature was 50 ° C, and the molding cycle was 100 seconds. Injection molding was performed under the conditions to obtain a molded product.

Using a spectrophotometer (trade name: U-4100 type) manufactured by Hitachi, Ltd., the transmittance of light in the wavelength range of 250 to 800 nm in the longitudinal direction of the molded product was measured, and the YI value was calculated.
(4) Treatment of recycle monomer 2,5-dimethylfuran contained in the recycle monomer was filled with a cross-linkable adsorption resin (XAD-2000 manufactured by Organo) according to, for example, JP-A-2001-122826. The flow rate was reduced by using a stationary phase. The organic acid was reduced by passing through a stationary phase filled with a styrenic weakly basic anion exchange resin (Amberlite IRA96SB manufactured by Rohm and Haas) according to, for example, JP-A No. 2004-123896.
[Example 1]
1 in 100 parts monomer mixture of 95% methyl methacrylate (MMA) and 5% methyl acrylate (MA) with a concentration of 2,5-dimethylfuran of less than 0.1 ppm and an organic acid concentration of less than 1 ppm. , 1-Bis (t-butylperoxy) 3,3,5-trimethylcyclohexane 0.005 part and n-octyl mercaptan 0.25 part were deoxygenated by a nitrogen substitution method.

  Subsequently, the deoxygenated monomer raw material solution was continuously supplied to the polymerization reactor at a rate of an average residence time of 2 hours and polymerized at a polymerization temperature of 135 ° C. to obtain a partially polymerized solution. The polymerization rate of the partially polymerized solution was 50%.

The obtained partially polymerized solution had a devolatilization part temperature set to 240 ° C., the devolatilization part reduced pressure was set to 1.3 to 11 kPa (10 to 80 torr) , and the extrusion temperature was set to 240 ° C. Was supplied into a devolatilizing extruder (manufactured by Nippon Steel Works, Ltd.), and the resulting polymer was pelletized while volatiles were devolatilized. The concentration of 2,5-dimethylfuran (DMFu) in the pellet was less than 0.1 ppm, and the concentration of organic acid was less than 1 ppm. Moreover, the YI value of the molded product obtained using the said pellet was 2.8.

  Note that the volatile-containing recovered material recovered by devolatilization was not used as a recycled raw material.

The abbreviations in Table 1 indicate the following compounds.
MMA: methyl methacrylate MA: methyl acrylate DMFu: 2,5-dimethylfuran [Examples 2 to 4, 7 and Comparative Examples 1 to 3]
An acrylic polymer and a molded product thereof were obtained in the same manner as in Example 1 except that MMA containing DMFu and organic acid at concentrations shown in Table 1 was used. Table 1 shows the evaluation results of the concentration of DMFu and organic acid in the obtained acrylic polymer and the YI value of the molded product.
[Example 5]
In the same manner as in Example 1, continuous polymerization and devolatilization extrusion were carried out continuously for 30 days.

  A volatile-containing recovered material that has been devolatilized from a devolatilizing extruder and continuously recovered is fixed with a cross-linked adsorption resin (trade name: XAD-2000) manufactured by Organo Corporation for removal of impurities. Liquid was passed through the phase at a space velocity (SV) of 5 / hour. Subsequently, the deoxygenated monomer was passed through the stationary phase packed with a styrene weakly basic anion exchange resin (trade name: Amberlite IRA96SB) manufactured by Rohm and Haas at a space velocity of SV = 10 / hour. Polymerization and pelletization were carried out continuously in the solution of the mixture.

  The concentration of DMFu in the monomer mixture into which the volatile-containing recovered material was continuously charged was 25 ppm (concentration 26.3 ppm in MMA), and the concentration of organic acid was 5 ppm (concentration in MMA 5.3 ppm). It was. The continuous operation multiplier at this time was 1. The calculation formula is as follows.

25 (ppm) × 10 ⁻⁶ × (273 + 240) (K) × 30 (day) = 0.38
Table 1 shows the evaluation results of the DMFu and organic acid concentrations in the acrylic polymer obtained on the 30th day of continuous operation and the YI value of the molded product.
[Example 6]
An acrylic polymer and its molded product were obtained in the same manner as in Example 5 except that the temperature of the devolatilization part in the devolatilization extruder was 290 ° C. The continuous operation multiplier at this time was 1.

Table 1 shows the evaluation results of the DMFu and organic acid concentrations in the acrylic polymer obtained on the 30th day of continuous operation and the YI value of the molded product.
[Comparative Example 4]
The volatile matter-containing recovered product that was devolatilized from the devolatilizing extruder and continuously recovered was not treated with a cross-linked adsorption resin and a styrenic weakly basic anion exchange resin. Other than that was carried out similarly to Example 5, and obtained the acrylic polymer and its molded article. The continuous operation multiplier at this time was 77. Table 1 shows the concentrations of DMFu and organic acid in MMA in the monomer raw material.

Table 1 shows the evaluation results of the DMFu and organic acid concentrations in the acrylic polymer obtained on the 30th day of continuous operation and the YI value of the molded product.
[Comparative Example 5]
An acrylic polymer and its molded product were obtained in the same manner as in Comparative Example 4 except that the temperature of the devolatilization part in the devolatilization extruder was 310 ° C. The continuous operation multiplier at this time was 77. Table 1 shows the concentrations of DMFu and organic acid in MMA in the monomer raw material.

  Table 1 shows the evaluation results of the DMFu and organic acid concentrations in the acrylic polymer obtained on the 30th day of continuous operation and the YI value of the molded product.

  The acrylic polymer obtained by the present invention exhibits good moldability, can give a molded product excellent in coloring resistance and thermal stability, and is suitable for various applications.

Claims (7)

  The monomer raw material for obtaining the acrylic polymer is supplied to a devolatilizing extruder with a partial polymerization solution obtained by continuous partial polymerization to complete the polymerization, and at the same time, volatiles are separated and removed. The concentration of 2,5-dimethylfuran introduced into the monomer raw material as a recycled raw material after passing the collected volatile-containing recovered material through a cross-linked adsorption resin and a weakly basic anion exchange resin is 0.2 ppm. The manufacturing method of the acrylic polymer which is the following and the density | concentration of the organic acid converted into methacrylic acid is 1 ppm or less. The method for producing an acrylic polymer according to claim 1 , wherein methyl methacrylate having a concentration of 2,5-dimethylfuran of 30 ppm or less is used as a monomer for obtaining the acrylic polymer. The acrylic polymer according to claim 1 or 2 , wherein the acrylic polymer is a polymer containing 90 to 100% by mass of methyl methacrylate units and 0 to 10% by mass of alkyl acrylate units having 1 to 8 carbon atoms. Method. The product of the numerical values of the concentration of 2,5-dimethylfuran in the monomer raw material (ppm × 10 ⁻⁶ ), the absolute temperature (K) of the devolatilization part in the devolatilization extruder and the continuous polymerization period (days) is 2. It is the following, The manufacturing method of the acrylic polymer in any one of Claims 1-3 . The temperature of the devolatilization part in a devolatilization extruder is 190-300 degreeC, The manufacturing method of the acrylic polymer in any one of Claims 1-4 . The method for producing an acrylic polymer according to any one of claims 1 to 5 , wherein the polymerization temperature is 100 to 180 ° C. The pressure reduction degree in a devolatilization extruder is 1.3-11 kPa , The manufacturing method of the acrylic polymer in any one of Claims 1-6 .