JPH0158204B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a fluoroalkyl methacrylate polymer having excellent heat resistance. Fluorine-containing resin is a material that has been used as a variety of functional materials, including heat-resistant and corrosion-resistant materials and high-performance dielectric materials, and its characteristic surface properties, optical properties,
It is functionally applied in various fields by taking advantage of its radiation sensitivity, permselectivity, electrical properties, and medical material properties. Among fluorine-containing polymers, polyfluoroalkyl methacrylate or copolymers containing fluoroalkyl methacrylate as the main component have optical properties such as low refractive index, water- and oil-repellent surface properties, and their weight. Radiation sensitivity based on the characteristic solubility of coalescence,
Furthermore, it is positioned as a special polymer with excellent hygroscopic properties and dimensional stability. One of the applications of such fluoroalkyl methacrylate polymers as industrial materials is to use polystyrene, polymethyl methacrylate, polycarbonate, etc. as core materials for optical transmission bodies that take advantage of their optical properties of low refractive index. However, the above-mentioned fluoroalkyl methacrylate polymer having a lower refractive index than the core material is used as the sheath material. In addition, resin molding materials can be mentioned as a use of these fluorocarbon resins, but detailed molding research has not been conducted regarding their use as resin molding materials because fluorocarbon resins are expensive. This is the current situation. When fluorine-containing resins or mixtures of them and general-purpose resins are melted at high temperatures and thermoformed, problems such as jetting properties and silver generation occur, resulting in inferior processed products. Particularly, in the case of mixed melt molding of a highly transparent methacrylic resin and a fluoroalkyl methacrylate polymer, the influence is significant, causing problems in quality and appearance. Furthermore, when the above-mentioned fluoroalkyl methacrylate polymer is thermoformed, a foaming phenomenon occurs along with the generation of silver, resulting in poor molding thermal stability. Therefore, the current situation is that low-temperature processing and processing in a low kneading state are forced, leaving problems with formability. The above-mentioned problems in thermoforming of fluorine-containing resins are considered to be due to thermal deterioration due to depolymerization during heating and melting, and are a phenomenon caused by foaming of the resulting monomer. For example, when compared to an ester of a non-fluorinated alcohol with the same number of carbon atoms, a fluorinated alcohol ester of methacrylic acid has a lower density of double bonds capable of radical polymerization, resulting in a molecular structure that is more susceptible to radical depolymerization. It's summery. In this sense, the polymer properties during the production of fluorine-containing resin polymers deteriorate with repeated thermal shaping, the degree of polymerization decreases, and the plasticizing effect of the fluorine-containing monomers produced after radical depolymerization. As a result, the properties of the fluorine-containing resin are significantly reduced. As a measure to prevent such thermal deterioration, a method of adding a deterioration inhibitor has been proposed, and a typical deterioration inhibitor is hindered phenol. However, although this method has good effects on heat resistance and prevention of depolymerization, problems arise with compatibility with fluorine-containing resins, dispersibility, and transparency, and the visible , has a defect in that it has a fatal adverse effect on transparent resin bodies because it has molecular absorption in the ultraviolet region. The present inventors have conducted extensive research to improve the above-mentioned drawbacks of fluoroalkyl methacrylate polymers, and have found that fluoroalkyl methacrylate monomers or monomer mixtures containing fluoroalkyl methacrylate as the main component are We discovered that a fluoroalkyl methacrylate polymer that maintains refractive index and transparency and has excellent heat resistance can be obtained by polymerizing it in the presence of a mercaptan having two or more mercapto groups in the molecule, and we have developed this book. The invention has been achieved. Fluorine-containing resin polymers are inherently prone to radical depolymerization during thermoforming processing, but by using the above mercaptan as a chain transfer agent, depolymerization of the resulting polymer is prevented, and heat resistance is improved. can be significantly improved. This is because when the mercaptan used as a chain transfer agent binds to the end of the polymer through a chain transfer reaction and becomes a thioether type, if an active mercapto group is present there, the radicals generated during thermoforming process. This is based on the idea that it works effectively as a starting point scavenger. For this reason, it is necessary for the mercaptan used as a chain transfer agent to have two or more mercapto groups in one molecule. As radical polymerization progresses, chain transfer occurs to one mercapto group of the mercaptan, and the other mercapto group becomes free at the end of the polymer, allowing it to remain active as a radical scavenger at the end of the resin polymer. Essentially, each mercapto group in a polyfunctional mercaptan has the same chain transfer agent function, but one mercapto group that once acted as a chain transfer agent is present at the polymer terminal with a thioether bond, but other mercapto groups The character of the mercapto group in the mercapto group is different from that in the low molecule before thioether bonding, and the free mercapto group present at the end of the polymerized polymer remains free as an active mercaptan with its degree of freedom of molecular movement largely restricted. I can't help it. This shows that the degree of uniform dispersion is higher than that obtained by simply mixing and melting these and the fluorine-containing polymer. The reliable reason for this is based on the fact that the more polyfunctional the mercaptan, the better the heat resistance. Examples of mercaptans containing two or more mercapto groups in one molecule used in the present invention include triethylene glycoldithiol, trimethylolpropanethioglycolate, pentaerythritol tetrathioglycolate, and trimethylolpropane-tris-β-mercaptopropane. Pionate, pentaerythritol tetrathiopropionate, mercaptoethyl borate, polyfunctional mercaptan-containing polymers produced from polyglycidyl methacrylate and thioglycolic acid, and the like. The amount of mercaptan added is 100% of the polymer.
0.01 to 5 parts by weight, preferably 0.05 to 5 parts by weight
2 parts by weight may be applied. The amount of mercaptan added is
This is because if it is less than 0.01 part by weight, the effect of improving heat resistance will not be sufficient, and if it exceeds 5 parts by weight, it will adversely affect transparency and strength. Examples of the fluoroalkyl methacrylate monomer used in the present invention include the general formula or general formula (In the formula, X is H, F or Cl, n is an integer of 1 to 6,
m is an integer of 1 to 10, l is an integer of 1 to 10, R ₁ and R ₂ represent H, CH ₃ , C ₂ H ₅ or CF ₃ . ) can be mentioned. In the present invention, specific examples of vinyl monomers copolymerizable with fluoroalkyl methacrylate include methyl methacrylate,
Ethyl methacrylate, propyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, glycidyl methacrylate, methacrylic acid, acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, benzyl acrylate, glycidyl methacrylate, glycidyl acrylate, styrene, α
-Methylstyrene, 2,4-dimethylstyrene,
p-chlorostyrene, 2,4-dichlorostyrene, p-methoxystyrene, acrylonitrile,
Examples include methacrylonitrile, vinyl acetate, methyl vinyl ketone, hydroxypropyl acrylate, and hydroxyethyl acrylate. Among them, methyl methacrylate is particularly preferred from the standpoint of providing a transparent copolymer. The content of these vinyl monomers in the copolymer can be 30% by weight or less of the fluorine-containing resin. If it exceeds 30% by weight, it is not preferable because it will adversely affect the properties of the fluoroalkyl polymethacrylate, such as heat resistance, low refraction, and transparency. Usual radical polymerization initiators can be used as the polymerization catalyst, and specific examples include di-tert-butyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, tert
-Butyl perphthalate, tert-butyl perbenzoate, methyl isobutyl ketone peroxide, lauroyl peroxide, cyclohexane peroxide, 2,5-dimethyl-2,5-di-
Organic peroxides such as tert-butylperoxyhexane, tert-butylperoctanoate, tert-butylperisobutyrate, tert-butylperoxyisopropyl carbonate, methyl 2,2'-azobisisobutyrate, 1,1 '-azobiscyclohexanecarbonitrile, 2-phenylazo-
2,4-dimethyl-4-methoxyvaleronitrile, 2-carbamoyl-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 2,2'-azobisisobutyronitrile, etc. The following azo compounds are mentioned. Polymerization methods include emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization, and bulk polymerization is preferred in order to obtain a highly pure polymer. The present invention will be specifically explained below with reference to Examples and Comparative Examples. In addition, all parts in the examples indicate parts by weight, and all percentages indicate weight %. Example 1 After mixing and dissolving 100 parts of 2,2,2-trifluoroethyl methacrylate, 2 parts of methyl methacrylate, and 0.5 part of triethylene glycoldithiol, azobisisobutyronitrile was added as a polymerization catalyst.
0.05 part was added and charged into a glass ampoule tube, and the tube was sealed under reduced pressure after repeated degassing and nitrogen substitution. A transparent polymer was obtained by heating and polymerizing in hot water at 70°C for 15 hours.
The polymerization conversion rate was 99%. The obtained polymer was crushed using a crusher and separated into 16 mesh passes and 32 mesh parts according to JIS Z8801 standard, and the measured temperature was measured.
A melt indexer flow length test was carried out under the conditions of 230°C and a load of 5 kg, and the obtained strands were shaped into pellets and subjected to a heat resistance test. Heat resistance test
Heated in an air atmosphere and nitrogen in a gear oven at 270°C, and measured the weight loss rate over time.
This was used for heat resistance evaluation. The evaluation results are shown in Table 1 together with other Examples and Comparative Examples. When this sample was made into a film and the refractive index was measured using an Atsube refractometer, it was 1.418, indicating that the film had excellent transparency. Examples 2 to 8, Comparative Examples 1 to 4 Polymerization was carried out in the same manner as in Example 1, except that mercaptan shown in Table 1 was used instead of triethylene glycol dithiol as a chain transfer agent, and pellets and films were prepared respectively. It was processed and evaluated.

[Table] Tan polyfunctional polymer In Comparative Example 3 (*2), after crushing the polymer obtained in Comparative Example 1, 0.1 part of 2,2'-methylenebis(4-methyl-6-tert-butylphenol) was added. When evaluated by mixing and adding strands, the transparency of the strands was insufficient and cloudiness was observed. Comparative Example 4 (*3) was evaluated by adding 0.1 part of 2,6-di-tert-butyl p-cresol to the polymer obtained in Comparative Example 1 after pulverizing it, and the transparency of the strands was evaluated. Although the results were good, there was an absorption region in the ultraviolet region. The evaluation results of heat resistance etc. are shown in Table 3. Examples 9 to 13 The procedure was carried out in the same manner as in Example 1, except that the types and charge ratios of fluoroalkyl methacrylate, copolymerized vinyl monomer, and chain transfer agent were changed as shown in Table 2. They were processed into pellets and films and their performance was evaluated, and the results are shown in Table 3. Example 14 After mixing and dissolving 100 parts of 2,2,2-trifluoroethyl methacrylate, 2 parts of methyl methacrylate, and 0.5 part of triethylene glycoldithiol, azobisisobutyronitrile was added as a polymerization catalyst.
0.05 part was added and dissolved. Meanwhile, in a 3L three-necked flask equipped with a stirrer and cooling tube, 200 parts of pure water, 0.005 part of partially saponified polymethacrylic acid, and sodium chloride.
0.5 parts were mixed, stirred and dissolved, and the previously prepared monomer mixture to which the polymerization catalyst had been added was added and dispersed, followed by heating and polymerization at 70° C. for 15 hours. Polymer is 100
It was a uniform pearl body of ~300μ. This polymer was molded into pellets and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3. Example 15 After mixing and dissolving 100 parts of 2,2,2-trifluoroethyl methacrylate, 2 parts of methyl methacrylate, and 0.5 part of triethylene glycoldithiol, azobisisobutyronitrile was added as a polymerization catalyst.
0.05 part was added and dissolved. On the other hand, 200 parts of pure water and 2 parts of sodium dodecyl sulfate were stirred and dissolved in a 3L three-necked flask equipped with a stirrer and a cooling tube, and the monomer mixture prepared earlier with the addition of the polymerization catalyst was added thereto. The emulsified state was heated and polymerized at 70°C for 10 hours.
After polymerization, 1 part of aluminum sulfate was added to obtain a coagulated powder at 90° C. After drying, pellets were evaluated in the same manner as in Example 1, and the evaluation results are shown in Table 3. The heat resistance evaluation (*4) in Table 3 indicates: 〇...good, △...fair, ×...poor.

【table】

【table】

[Table] As shown in the examples above, the fluoroalkyl methacrylate polymer produced according to the present invention has excellent weather resistance, transparency, and formability, as well as excellent heat resistance. In addition to being used as a sheath material, it is also used for film materials that retain the characteristics of fluorine-containing polymers, such as oil repellency, water repellency, and chemical stain resistance, and for resin molding materials that can withstand fine molding processes. Alternatively, it can be applied to materials that require precision processing such as abrasive cutting.

Claims (1)

[Claims] 1 70% by weight or more of fluoroalkyl methacrylate monomer or fluoroalkyl methacrylate and 30% by weight of vinyl monomer copolymerizable with it
A method for producing a fluoroalkyl methacrylate polymer having excellent heat resistance, which comprises adding a polymerization catalyst and a mercaptan having two or more mercapto groups in one molecule to the following mixture for polymerization.