JP2000159822A - Production of methyl methacrylate based polymer bead - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing methyl methacrylate-based polymer beads having an average particle diameter of not smaller than 400 μm suitable for expansion molding. SOLUTION: In producing a methyl methacrylate based polymer by subjecting a monofunctional monomer having methyl methacrylate as the major component to suspension polymerization with the use of a radical polymerization initiator in an aqueous medium in the copresence of a copolymerizable polyfunctional monomer and a chain transfer agent, the polymerization is effected with an amount of the chain transfer agent of 2.5×10-5 mol to 5×10-3 mol per mol of the monofunctional monomer and an amount of the copolymerizable polyfunctional monomer in terms of the number of functional groups of 1×10-5 mol to [the chain transfer agent (mol) minus 2.5×10-4 mol] per mol of the monofunctional monomer in the presence of a suspension stabilizer of a partially saponified polyvinyl acetate having a concentration in the aqueous medium of 0.01-0.05 wt.%, a saponification degree of 85-90 and a viscosity of 20-110 mPa.s (4% aqueous solution, 20 deg.C) and at least one compound selected from a borate salt, a carbonate salt, a phosphate salt and a sulfate salt which has a concentration in the aqueous medium of 0.1-10 wt.% to form a polymer having an intrinsic viscosity [η] of 0.25-1.5 dl/g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a methyl methacrylate polymer bead having a larger particle size than a known methyl methacrylate polymer. The present invention relates to a method for producing methyl methacrylate polymer beads.

[0002]

2. Description of the Related Art Methyl methacrylate-based polymers are rigid, have excellent transparency, and are also excellent in weather resistance.
It is widely used as molded articles such as spectacle lenses and light guides, and further extruded and formed as extruded plates such as signboards and nameplates.
On the other hand, a methyl (meth) acrylate-based polymer is required to have both high fluidity and high strength during melt stretching.
At present, it is not suitable for materials for blow molding and foam molding, and is not used in these fields.

[0003] The present inventors have conducted intensive studies to provide a methyl methacrylate polymer having excellent melt fluidity which can be applied to such fields, and as a result, have found that it has a branched structure and a weight average molecular weight of 80,000 to 80,000. It has been found that a methyl methacrylate-based polymer having a branched structure having a molecular weight between branch points defined by using a Z-average molecular weight of from 400,000 to 400,000 and having a molecular weight between 30,000 to 500,000 can satisfy the above characteristics. An application was filed as Hei 7-280235 (Japanese Patent Application Laid-Open No. Hei 8-208746). by the way,
As the foam molding material, the larger the resin particle diameter containing the foaming agent is, the more the foaming agent contributing to foaming is less likely to volatilize from the particle surface than in the case of the smaller one, and it is considered that molding with a high expansion ratio can be performed. However, in the polymerization of styrene and the like, a sparingly soluble inorganic salt fine powder and an anionic surfactant, and further, these and polyvinyl alcohol, polyvinyl pyrrolidone,
Although a method for producing a resin having a large particle diameter by using a water-soluble polymer such as methyl cellulose as a suspension stabilizer is known, it is not known for a methyl methacrylate resin.

[0004]

In view of such circumstances, the present inventors have readily impregnated resin with a foaming agent,
As a result of intensive studies aimed at obtaining a methyl methacrylate-based resin having a large particle diameter and low gas release, a specific suspension was required for suspension polymerization of a monomer containing methyl methacrylate as a main component in an aqueous medium. When a suspension stabilizer and a specific suspension aid are polymerized in combination, it has been found that methyl methacrylate-based polymer beads having a large particle diameter of about 400 μm or more satisfying the above objects can be obtained. The invention has been completed.

[0005]

That is, the present invention relates to a method of preparing a monofunctional monomer containing methyl methacrylate as a main component by using a radical polymerization initiator to form a copolymerizable polyfunctional monomer and a chain transfer agent. In the coexistence, when producing a methyl methacrylate polymer by suspension polymerization in an aqueous medium, a saponification degree of 85 to 90% in an amount such that the concentration in the aqueous medium becomes 0.01 to 0.05% by weight; Viscosity 20 to 110 mPa · S (4
% Aqueous solution, 20 ° C.) and a borate, carbonate, phosphate and sulfate in such an amount that the concentration in the aqueous medium is 0.1 to 10% by weight. Suspension polymerization in the presence of at least one compound selected from the group consisting of
An object of the present invention is to provide a method for producing a methyl methacrylate polymer bead having a size of 0 μm or more.

Further, the present invention provides a method for preparing a monofunctional monomer containing methyl methacrylate as a main component in an aqueous medium in the presence of a copolymerizable polyfunctional monomer and a chain transfer agent using a radical polymerization initiator. When producing a methyl methacrylate polymer by suspension polymerization, the amount of the chain transfer agent is from 2.5 × 10 ⁻⁵ mol to 5 × per mol of the monofunctional monomer.
10 ⁻³ mol, the amount of the copolymerizable polyfunctional monomer is 1 × 10 ⁻⁵ to 1 × 10 ⁻⁵ per 1 mol of the monofunctional monomer.
{Chain transfer agent (mol) -2.5 × 10 ^-4 } The amount of saponification is 85 to 90% and the viscosity is in the amount of 0.01 to 0.05% by weight in the aqueous medium, and the viscosity is 2.5 × 10 ^-4 mol 20 ~ 110mP
a · S (4% aqueous solution, 20 ° C.), a suspension stabilizer composed of partially saponified polyvinyl acetate;
An average particle diameter characterized by being subjected to suspension polymerization in the presence of at least one compound selected from the group consisting of borates, carbonates, phosphates and sulfates in an amount of 10 to 10% by weight. An object of the present invention is to provide a method for producing a methyl methacrylate polymer bead having a size of 400 μm or more.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The methyl methacrylate polymer beads of the present invention,
Substantially spherical particles of a monofunctional monomer containing methyl methacrylate as a main component and a polymer of a polyfunctional monomer copolymerizable therewith with an average particle diameter of 400 μm or more.
Spherical particles are not discotic or elliptical in shape but are substantially spherical (for example, the average value of the major and minor degrees (minor axis / major axis) of 100 randomly selected particles is preferably about 0.7 or more, preferably About 0.8 or more].

In the present invention, the average particle size is defined as a sonic vibration type fully automatic sieving device (manufactured by Seishin Enterprise) or an electromagnetic vibration type sieving device (Mitamura Riken Kogyo Co., Ltd.).
Means the average particle size of 50% of the cumulative weight obtained by using the above formula. (Based on JIS Z-8801 (1982))

In the production method of the present invention, the monofunctional monomer containing methyl methacrylate as a main component refers to methyl methacrylate alone or 50% by weight or more, preferably 70% by weight or more of methyl methacrylate. It is a mixture with a copolymerizable monofunctional unsaturated monomer. 50 methyl methacrylate
When the amount is less than the weight percentage, transparency and mechanical strength, which are characteristics of a so-called methyl methacrylate polymer, are hardly exhibited.

The monofunctional unsaturated monomer copolymerizable with methyl methacrylate includes, for example, ethyl methacrylate,
Methacrylates such as propyl methacrylate, butyl methacrylate, benzyl methacrylate: acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate: acrylic acid, methacrylic Acids, unsaturated carboxylic acids such as maleic acid and itaconic acid, and acid anhydrides such as maleic anhydride and itaconic anhydride: 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, monoglycerol acrylate, 2-methacrylic acid 2- Esters having a hydroxyl group such as hydroxyethyl, hydroxypropyl methacrylate and monoglycerol methacrylate: acrylamide, methacrylamide and diacetone acrylamide. Acrylonitrile,
Nitriles such as methacrylonitrile: Nitrogen-containing monomers such as dimethylaminoethyl methacrylate: Epoxy group-containing monomers such as allyl glycidyl ether, glycidyl acrylate, and glycidyl methacrylate.

Polyfunctional monomers copolymerizable with a monofunctional monomer containing methyl methacrylate as a main component include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and triethylene glycol di (meth) acrylate. ) Ethylene glycol such as acrylate and tetraethylene glycol di (meth) acrylate, or an oligomer thereof, in which both terminal hydroxyl groups are esterified with acrylic acid or methacrylic acid; neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate
Acrylic acid or butanediol di (meth) acrylate or the like obtained by esterifying the hydroxyl group of a dihydric alcohol with acrylic acid or methacrylic acid; a polyhydric alcohol such as trimethylolpropane or pentaerythritol or a derivative of these polyhydric alcohols with acrylic acid or Examples thereof include those esterified with methacrylic acid.

In the present invention, a monofunctional monomer containing methyl methacrylate as a main component and a polyfunctional monomer copolymerizable therewith are used in an aqueous medium having a concentration of 0.01 to 0.05% by weight.
Degree of saponification 85-90%, viscosity 20-110 m
A suspension stabilizer composed of partially saponified polyvinyl acetate having a Pa · S (4% aqueous solution, 20 ° C.) and a concentration of 0.1% in an aqueous medium;
The suspension polymerization is carried out in the presence of at least one compound selected from the group consisting of borate, carbonate, phosphate and sulfate in an amount of 1 to 10% by weight.

When the saponification degree, viscosity and amount of the suspension stabilizer comprising partially saponified polyvinyl acetate used in the present invention are out of the above ranges, the polymerization becomes unstable and the resulting polymer beads are not spherical, Agglomerated particles or particles having irregular particle shapes may occur, or a large number of fine granular polymer beads may be generated, and the average particle diameter may be reduced.

In the present invention, boric acid having a concentration in an aqueous medium of 0.1 to 10% by weight, preferably 0.3 to 3% by weight, together with a specific partially saponified polyvinyl acetate suspension stabilizer is used. The suspension polymerization is essential in the presence of at least one compound selected from the group consisting of salts, carbonates, phosphates and sulfates. Examples of the borate, carbonate, phosphate and sulfate include sodium borate, potassium carbonate, sodium carbonate, sodium hydrogen carbonate, sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium sulfate and the like. Can be The use of phosphates such as sodium phosphate and disodium hydrogen phosphate is recommended. If the concentration of these compounds in the aqueous medium is out of the above range, the polymerization system becomes unstable, the number of aggregated particles increases, and the particle shape becomes uneven.

The ratio of aqueous medium to monomer or monomer mixture ranges from 1: 1 to 5: 1, preferably from 1: 1 to 3: 1. If the amount of the aqueous medium is too small, the dispersion of the monomer tends to be non-uniform and the polymerization system becomes unstable. If the amount is too large, a large number of fine particulate polymer beads are formed and the average particle diameter becomes small.

The temperature for the polymerization may be about 60 to 120 ° C., a temperature suitable for the polymerization initiator used, and the stirring conditions may be the same as those for producing methyl methacrylate polymer beads by ordinary suspension polymerization. Is fine. As the polymerization apparatus, a polymerization vessel equipped with a stirrer with a well-known stirring blade such as a turbine blade, a Faudler blade, a propeller blade, a blue margin blade, etc. is used, and the vessel is generally equipped with a baffle. is there. After completion of the suspension polymerization, polymer beads can be obtained by washing, dehydrating and drying by a well-known method.

The methyl methacrylate polymer beads of the present invention are not particularly limited, but have a branched structure excellent in melt flowability already known from JP-A-8-208746, and have a weight average Molecular weight (Mw) 80,000 ~
400,000, preferably 150,000 to 300,000, and the molecular weight between branch points (Mz) defined using the Z average molecular weight (Mz).
It is recommended to apply methyl methacrylate resin particles having b) of 30,000 to 500,000, preferably 50,000 to 200,000.

When the Mw is in the above range, the polymer is excellent in mechanical strength, the strength of a foam obtained by foaming a methyl methacrylate-based polymer bead containing the polymer as a component is excellent, and the M Excellent in fusing properties. When the molecular weight between branch points (Mzb) is in the above range, the polymer is excellent in foaming performance, mechanical strength, and appearance of a molded product.

Here, Mw and Mz are values determined by gel permeation chromatography (GPC) and a differential refractometer. The method of obtaining this is, for example, 19
1984 edition, "Polymer Characteristic Analysis" (Kyoritsu Shuppan), p.
It is described on page 55.

The molecular weight between branch points means an average value of the molecular weight from a branch point to the next branch point in a polymer having a branched structure. The molecular weight between branch points (Mzb) defined using this Z-average molecular weight can be found in The Rubber Association of Japan, 45th
Volume 2, No. 105, p. 105-118, based on the description in "Characterization".

[0021]

[Equation 1] {[η ₁ ] / [η ₂ ]} ^10/6 = ｛(1 + Bz /
6) ^0.5 + 4Bz / 3π｝ ^-0.5

[0022]

## EQU2 ## Mzb = Mz / Bz

In the above formula 1, η ₁ is a measurement object obtained by using a universal calibration curve showing the relationship between the intrinsic viscosity and the absolute molecular weight with respect to the GPC elution time of a standard sample of a linear methyl methacrylate polymer. In the calibration curve showing the relationship between the intrinsic viscosity and the absolute molecular weight of the polymer, the molecular weight is the intrinsic viscosity corresponding to the Mz value. η ₂ is the limiting viscosity corresponding to the same molecular weight Mz value as the polymer to be measured in the calibration curve showing the relationship between the limiting viscosity and the absolute molecular weight of the linear methyl methacrylate polymer standard sample.
Bz is the number of branch points in the Z average molecular weight Mz.

In the methyl methacrylate-based polymer, the proportion of the polymer having a molecular weight of 300,000 or more in the polymer has a reduced viscosity at 25 ° C. in chloroform of 0.7.
dl / g or less, Δ [14 × the reduced viscosity value−6.
8] to [14 × the reduced viscosity value + 11 · 2]｝ (% by weight)
When the reduced viscosity is 0.7 dl / g or more, ｛[4
0 × the reduced viscosity value−25] to [40 × the reduced viscosity value−
7]｝ (% by weight) is preferable. The reduced viscosity described in the present invention is a value at a solution concentration of the polymer to be measured at 1 g / dl. When the ratio of the molecular weight of the methyl methacrylate polymer having a branched structure of 300,000 or more is within the above range, the flowability of the methyl methacrylate polymer and the balance between the tensile strength at the time of melting are excellent. Thus, a good foam can be obtained due to the excellent balance between the fluidity of the resin composition obtained by using the resin composition and the strength during melt stretching. The degree of crosslinking of the methyl methacrylate polymer having such a branched structure is usually expressed as a gel fraction (% by weight of an unnecessary portion of acetone based on the total weight of the polymer) and is usually 3%.
Or less, preferably 1% or less, more preferably about 0%.

The methyl methacrylate polymer having a large particle diameter according to the present invention having such physical properties can be obtained by copolymerizing a monofunctional monomer containing methyl methacrylate as a main component by using a radical polymerization initiator. When producing a methyl methacrylate polymer by suspension polymerization in an aqueous medium in the presence of a polyfunctional monomer and a chain transfer agent, the moles of the chain transfer agent per mole of the monofunctional monomer 2.5 × 10
^-5 mol to 5 × 10 ^-3 mol, and the amount of the copolymerizable polyfunctional monomer is 1 per 1 mol of the monofunctional monomer.
× 10 ⁻⁵ to {the chain transfer agent (mol) −2.5 × 10 ⁻⁴ }
Molar amount, the concentration in the aqueous medium is from 0.01 to 0.0
A saponification degree of 85 to 90% and a viscosity of 20 to 5% by weight.
A suspension stabilizer consisting of partially saponified polyvinyl acetate of 110 mPa · S (4% aqueous solution, 20 ° C.), a borate and a carbonate having a concentration of 0.1 to 10% by weight in an aqueous medium;
It is obtained by suspension polymerization in the presence of at least one compound selected from the group consisting of phosphates and sulfates.

In the above production method, the amount of the polyfunctional monomer is 1 × 1 in terms of the number of functional groups per mole of the monofunctional monomer.
The amount is from 0 ^-5 to {the chain transfer agent (mol) -2.5 × 10 ^-4 } mol. That is, depending on the amount of the chain transfer agent described below, even when {the chain transfer agent (mol) -2.5 × 10 ⁻⁴ } mol is less than 1 × 10 ⁻⁵ mol, 1 ×
10 ^-5 is required. When the number of functional groups is less than 1 × 10 ⁻⁵ mol, the resulting resin has low fluidity at a high shear rate, and has insufficient solvent resistance. On the other hand, if the amount of the chain transfer agent (mol) exceeds 2.5 × 10 ^-4 mol, the resulting resin has low melt fluidity and low moldability.

The radical polymerization initiator may be any of those known for polymerization of vinyl monomers. For example, 2,2
Azo compounds such as' -azobis (2,4-dimethylvaleronitrile), azobisisobutyronitrile, dimethyl-2,2'-azobisisobutyrate; t-butylperoxypivalate, t-butylperoxy Peroxyesters such as 2-ethylhexanoate and cumylperoxy 2-ethylhexanoate; diacyl peroxides such as diacyl peroxide such as di-3,5,5-trimethylhexanoyl peroxide and dilauroyl peroxide Organic peroxide, bifunctional 1,1-bis (t
-Butylperoxy) 3,3,5-trimethylcyclohexane, di-t-butylperoxytrimethyladipate, trifunctional tris- (t-butylperoxy) triazine, tetrafunctional 2,2-bis (4,4- Examples thereof include di-t-butylperoxycyclohexyl) propane, and one or more of these are used. The amount of the radical polymerization initiator to be used is usually 0.001 to 100 parts by weight of the monomer or the monomer mixture.
About 1 part by weight, preferably 0.01 to 0.7 part by weight.

In the above-mentioned production method, the chain transfer agent may be a known one used for the polymerization of methyl methacrylate. Among these, there are a monofunctional chain transfer agent having one chain transfer functional group and a polyfunctional chain transfer agent having two or more chain transfer functional groups.

Examples of the monofunctional chain transfer agent include alkyl mercaptans, thioglycolates, 3-mercaptopropionates, thiophenols, alkyl sulfides, alkyl disulfides, α-
Methylstyrene dimer and the like are preferable, and alkylmercaptans and 3-mercaptopropionate are preferable.

As the polyfunctional chain transfer agent, polyhydric alcohol hydroxyl groups such as ethylene glycol, neopentyl glycol, trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol and sorbitol can be used to convert thioglycolic acid or 3 -Esterified with mercaptopropionic acid.

The amount of the chain transfer agent is usually 2.5 × 10 ^-4 mol to 5 × 10 ^-3 mol per mol of the monofunctional monomer. If it is less than 2.5 × 10 ^-4 mol, the obtained methacrylic resin will have an excessively large [η], and the melt fluidity will be low. On the other hand, if it exceeds 5 × 10 ^-3 mol, [η] becomes too small, and the mechanical strength of the obtained methacrylic resin becomes low.

The intrinsic viscosity [η] of the methacrylic resin obtained by the above production method is 0.25 to 1.5 dl / g. If [η] is less than 0.25 dl / g, the mechanical strength and solvent resistance of the resin cannot be sufficient. Also,
If it is higher than 1.5 dl / g, the melt fluidity becomes too low and the moldability decreases.

The intrinsic viscosity [η] of the methacrylic resin is generally governed mainly by the concentration of the polyfunctional monomer used, the concentration of the chain transfer agent and the concentration of the radical initiator. The concentration of the radical initiator may be in the above-mentioned concentration range. Therefore, [η] is appropriately changed within the above-mentioned concentration range of the polyfunctional monomer and within the range of the concentration of the chain transfer agent so as to be adjusted to the above-mentioned [η]. This can easily be set with a few trials.

In the method for producing methyl methacrylate polymer beads (having a branched structure) of the present invention, a well-known suspension polymerization method can be applied, except that the above-mentioned conditions are satisfied. That is, in the aqueous medium, the above-mentioned monomer having methyl methacrylate as a main component, a polymerization initiator, a chain transfer agent and a copolymerizable polyfunctional monomer, and, if necessary, a release agent,
In this method, a stabilizer, a colorant, an ultraviolet absorber, an antioxidant, a light diffusing material, a plasticizer and the like are suspended and polymerized. The ratio of aqueous medium to monomer or monomer mixture is from 1: 1 to 5:
1, preferably in the range of 1: 1 to 3: 1. The temperature condition for the polymerization is about 60 to 120 ° C., which is a temperature suitable for the polymerization initiator used. After completion of the suspension polymerization, it can be washed, dehydrated, and dried by a known method before use.

[0035]

The methyl methacrylate polymer beads obtained by the method of the present invention described above in detail have a large average particle diameter of usually more than 400 μm, have little outgassing during foam molding, and have a high expansion ratio. In the production method of the present invention, when obtaining a methyl methacrylate polymer beads having a specific branched structure, the obtained methyl methacrylate polymer beads are It enables the production of a foam having a high expansion ratio, uniform foam cells and good appearance, and its industrial utility value is extremely large as a buffer packaging material, a heat insulating material, and a material for civil engineering.

[0036]

The present invention will be described below in detail with reference to examples.

Example 1 In a 200-liter SUS autoclave, 95 parts by weight of methyl methacrylate, 5 parts by weight of methyl acrylate,
0.15 parts by weight of 1,6-hexanediol diacrylate, 0.3 parts by weight of lauroyl peroxide, 0.4 parts by weight of n-dodecyl mercaptan, 150 parts by weight of ion-exchanged water, saponification degree 88%, viscosity 90 mPa · S ( 0.03 part by weight of a partially saponified polyvinyl acetate (4% aqueous solution, 20 ° C.), 4.5 parts by weight of disodium hydrogen phosphate / heptahydrate (2.384 parts by weight in terms of pure product: concentration in an aqueous medium: 1. (59% by weight), and the mixture was heated and heated to start polymerization at 80 ° C. After 120 minutes, polymerization was carried out at 100 ° C for 60 minutes. After the polymerization, washing, dehydration and drying were performed to obtain polymer beads. The obtained polymer beads had an average particle diameter of 830 μm and a spherical particle shape (length: 0.8 or more).

COMPARATIVE EXAMPLE 1 0.015 parts by weight of disodium hydrogen phosphate heptahydrate (0.0079 parts by weight in terms of pure product: concentration of 0.1 in an aqueous medium)
Polymerization was carried out in the same manner as in Example 1 except for using 0053% by weight to obtain polymer beads having an average particle diameter of 1150 μm.
In many cases, the particle diameters were irregular and not spherical (length: 0.66).

Comparative Example 2 Polymerization was carried out in the same manner as in Example 1 except that disodium hydrogen phosphate / heptahydrate was not used. The average particle size of the obtained polymer beads was 1320 μm, the particle size was irregular, and many were not spherical (length / shortness: 0.60).

Comparative Example 3 Saponification degree: 88%, viscosity: 90 mPa · S (4% aqueous solution, 2
0 ° C) instead of partially saponified polyvinyl acetate, with a saponification degree of 83% and a viscosity of 21 mPa · S (4% aqueous solution, 20 ° C)
Polymerization was carried out in the same manner as in Example 1 except that 0.03 parts by weight of the partially saponified polyvinyl acetate was used. As a result, aggregation occurred after 80 minutes, and polymer beads were not obtained.

Comparative Example 4 A saponification degree of 88% and a viscosity of 90 mPa · S (4% aqueous solution, 2
0 ° C), instead of partially saponified polyvinyl acetate, a degree of saponification of 99% and a viscosity of 70 mPa · S (4% aqueous solution, 20 ° C)
Polymerization was carried out in the same manner as in Example 1 except that 0.04 part by weight of the polyvinyl alcohol was used. As a result, aggregation occurred after 90 minutes, and polymer beads were not obtained.

Example 2 Same as Example 1 except that instead of disodium hydrogen phosphate heptahydrate, 2.25 parts by weight of trisodium phosphate (concentration in an aqueous medium: 1.5% by weight) was used. Was polymerized. The obtained polymer beads had an average particle diameter of 680 μm and a spherical particle shape (length: 0.8 or more).

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J011 AA08 JA03 JA04 JA06 JB07 JB26 NB03 4J100 AG15P AJ02P AJ08P AJ09P AK31P AK32P AL03P AL04P AL08P AL09P AL10P AL62Q AL63Q AL66Q AM02P AM15P AM03PBA03 BA04P FA21 JA58 JA67

Claims (5)

[Claims] 1. A monofunctional monomer containing methyl methacrylate as a main component is suspended in an aqueous medium using a radical polymerization initiator in the presence of a copolymerizable polyfunctional monomer and a chain transfer agent. In producing a methyl methacrylate polymer by polymerization, a saponification degree of 85 to 90% and a viscosity of 20 to 11 are used so that the concentration in the aqueous medium becomes 0.01 to 0.05% by weight.
0 mPa · S (4% aqueous solution, 20 ° C.), a suspension stabilizer consisting of partially saponified polyvinyl acetate, and borate, carbonate, phosphorus having an amount of 0.1 to 10% by weight in an aqueous medium A method for producing methyl methacrylate polymer beads having an average particle diameter of 400 μm or more, wherein suspension polymerization is carried out in the presence of at least one compound selected from the group consisting of acid salts and sulfates. 2. A monofunctional monomer containing methyl methacrylate as a main component is suspended in an aqueous medium using a radical polymerization initiator in the presence of a copolymerizable polyfunctional monomer and a chain transfer agent. When producing a methyl methacrylate polymer by polymerization, the amount of the chain transfer agent is from 2.5 × 10 ⁻⁵ mol to 5 × 10 ⁻³ mol per mol of the monofunctional monomer. The amount of the polymerizable polyfunctional monomer is 1 × 10 ⁻⁵ to {the chain transfer agent (mol) −2.5 × 10 ⁻⁴ } mol per 1 mol of the monofunctional monomer. The saponification degree 8 is such that the concentration in the aqueous medium becomes 0.01 to 0.05% by weight.
A suspension stabilizer consisting of partially saponified polyvinyl acetate having a viscosity of 5 to 90% and a viscosity of 20 to 110 mPa · S (4% aqueous solution, 20 ° C.) and an amount of a concentration of 0.1 to 10% by weight in an aqueous medium. Suspension polymerization in the presence of at least one compound selected from the group consisting of borates, carbonates, phosphates and sulfates, wherein the average particle diameter is 400 μm
A method for producing the above methyl methacrylate polymer beads. 3. A phosphate salt comprising disodium hydrogen phosphate, dipotassium hydrogen phosphate, trisodium phosphate and phosphoric acid.
The method for producing methyl methacrylate polymer beads according to claim 1 or 2, wherein the beads are at least one selected from the group consisting of potassium. 4. A methacryl having a branched structure in which the weight average molecular weight of the methyl methacrylate polymer beads is 80,000 to 400,000 and the molecular weight between branch points defined by using the Z average molecular weight is 30,000 to 500,000. 4. The method for producing a methyl methacrylate polymer bead according to claim 1, wherein the bead is a methyl methacrylate polymer bead. 5. The methyl methacrylate polymer having a branched structure, when the ratio of the polymer having a molecular weight of 300,000 or more to the polymer has a reduced viscosity of 0.7 dl / g or less, Δ [ 14 × the reduced viscosity value -6.8] to [14 × the reduced viscosity value + 11.2]｝ (% by weight), and when the reduced viscosity is 0.7 or more, {40 × the reduced viscosity value -25] ~
The method for producing methyl methacrylate polymer beads according to any one of claims 1 to 4, wherein [40 x reduced viscosity value-7] (% by weight).