JPS5951573B2 - Method for producing polymer beads coated with an inorganic filler layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing methyl methacrylate polymer beads coated with a uniform layer of inorganic filler.

Methyl methacrylate polymer is a type of plastic that is widely used as a molding material, but it is also used as an inorganic filler such as barium sulfate, titanium oxide, and calcium carbonate when used for manufacturing lighting covers, signboards, etc. It is often used by blending powders such as: as white pigments.

Usually, such a plate-shaped molded body of a white pigment-containing methyl methacrylate polymer is manufactured by a monomer gear stator sintering method, but in recent years, manufacturing has come to be performed by a melt extrusion method.

In this melt extrusion method, for example, the T-die method, the extruded plate is manufactured using emulsion polymerization or suspension polymerization, in which particles with a particle size of 0.1
Polymer beads of about 0.5 mm are produced, blended with necessary pigments and coloring agents, and then extruded using an extruder. However, when extruding such a compound using a large single-screw extruder with a cylinder diameter of 90 mm or more, extrusion may become unstable due to unstable feeding in the raw material supply section of the extruder, slippage occurring inside the extruder, etc. This method has drawbacks such as non-uniformity in discharge amount and hunting phenomena in resin pressure and power, which often results in deterioration of quality and reduction in efficiency.

5 In order to improve these drawbacks, polymer beads are blended with a large amount of inorganic filler powder, this blend is once melted and pelletized to form a so-called masterbatch, and then methacrylic acid is added to the masterbatch. It has been proposed to reblend the methyl polymer and use it as a raw material for forming extruded plates.

However, with this method, it is necessary to use special equipment such as a kneader or a twin-screw extruder to produce the masterbatch, and there are also variations in pigment concentration and classification phenomena that occur during the production of the masterbatch. It was not possible to completely eliminate color spots and color instability. The present inventors have overcome the drawbacks of such conventional methods and developed a polymer bead composition that can produce molded products of good quality without color spots or unstable color tone by melt extrusion. As a result of intensive research, we found that bead-shaped masterbatches, or master beads, can be easily prepared by partially swelling the surface of methyl methacrylate polymer beads and then uniformly depositing inorganic filler powder on this surface. We have discovered that by finishing the surface condition of these master beads uniformly and smoothly, the stability and extrusion ability of subsequent extrusion molding can be dramatically improved.Based on this knowledge, we have created the present invention. It came to this.

That is, in the present invention, in coating the surface of methyl methacrylate polymer beads with an inorganic filler, based on 100 parts by weight of methyl methacrylate polymer beads, (a) the general formula (in which R1 is a hydrogen atom) 0.2 to 2.0 parts by weight of an acrylic ester or methacrylic ester represented by (or methyl group, R2 is a lower alkyl group) and (b)
General formula R3OOC-(CH2)n-COOR4,. ．． (
) (in the formula, R3 and R4 are lower alkyl groups, n is 4j ~
It is an integer of 8.

0.2 to 2.5 parts by weight of dicarboxylic acid ester represented by ) is added and stirred at high speed to form a swollen state on the surface of the polymer beads, and then an inorganic filler powder is added and further stirred to form beads. The present invention provides a method for producing methyl methacrylate polymer beads coated with a uniform inorganic filler layer, which is characterized by adhering the same to the surface of the polymer.

The methyl methacrylate polymer used as beads in the present invention includes ordinary polymethyl methacrylate obtained by polymerizing methyl methacrylate alone in the presence of a radical polymerization catalyst, as well as comonomers such as methyl acrylate and butyl acrylate. It is a methyl metatallylate copolymer containing one or more of the following within a range of 15% by weight or less, and usually,
Those having a molecular weight of about 50,000 to 200,000 are preferable.

These polymers are used in the form of beads having an average particle diameter of 0.1 to 0.5 mm by emulsion or suspension polymerization in an aqueous medium. The average particle size of these beads is not necessarily limited to the above range, and high-speed stirring is possible.
Any particles may be used as long as they have a particle size suitable as an extrusion raw material. Next, as the acrylic ester represented by the general formula (1), the ester moiety is composed of an alkyl group having 1 to 4 carbon atoms, such as methyl acylate, ethyl acylate, propyl acrylate, butyl acylate, etc. Examples of the methacrylate ester include methyl methacrylate, ethyl methacrylate, methacrylate, and butyl methacrylate.

These esters are preferably used with a purity of 95% or higher. Further, these esters may be used alone or in combination of two or more. Examples of the dicarboxylic acid ester represented by the general formula () include dibutyl adipate, diisophyl adipate, diethyl adipate, dimethyl sebacate, methylethyl sebacate, diisooctyl sebacate, and the like.

It is preferable that these esters have a purity of 95% or more and are used alone or in combination of two or more. In the method of the present invention, the amount of the compound of general formula (1) and the compound of general formula () to be used is such that the surface of the methyl metatallylate polymer beads can be partially treated within the range of industrially practicable treatment temperature and treatment time. The amount must be an appropriate amount to swell the inorganic filler powder uniformly and smoothly, and this amount is based on the general formula (1) per 100 parts by weight of the polymer beads. 0.2 to 2.0 parts by weight for the compound of formula (), 0.2 to 2.5 parts by weight for the compound of general formula ()
It has been experimentally confirmed that the amount is within the range of parts by weight. Furthermore, the inorganic filler powder used in the method of the present invention is a powder of an inorganic substance commonly used as a white pigment, such as barium sulfate, titanium oxide, calcium carbonate, or talc, with an average particle size of 20 μm or less, preferably 10 μm or less. I can give it to you.

In order to suitably carry out the method of the present invention, first, methyl methacrylate polymer beads are stirred at high speed using a pen shell mixer type powder stirrer, and a mixture of the general formula (
By adding necessary amounts of the compound I) and the compound of general formula (1), either separately or as a mixture in advance, the surface of the polymeric resin 11 is uniformly swollen.
At this time, it is preferable to replace the inside of the container with nitrogen before adding each compound. The treatment temperature at this time is usually in the range of 0°C to 60°C, preferably 20°C to 40°C. For example, at a temperature of 20°C to 40°C. Stirring is started, and the compound of the general formula (I) and the compound of the general formula '(1) are immediately added and stirred for about 5 minutes, and the internal temperature rises to 40°C to 60°C.
The stirring time at this time is related to the rotation speed, but is 20
When using a circumferential speed of ~50 m/Sec, a range between 1 and 3 minutes is appropriate. After beads with partially swollen surfaces are formed in this manner, the inorganic filler powder is gradually added while stirring is continued. At this time, coloring agents and other additives may be added as desired.・The time required for stirring depends on conditions such as the type of inorganic filler, the amount used, the properties of the beads, the type of compound used for swelling, the amount used, and the processing temperature, but it is usually 10 to 20 minutes. is sufficient. Completion of the coating can be judged by the fact that the suspended state of dust due to agitation has subsided. In this way, methyl methacrylate polymer beads whose surfaces are coated with a uniform inorganic filler layer can be obtained, but these beads do not simply have an inorganic filler layer formed on the surface of the beads; The beads have a structure in which a portion of the inorganic filler is embedded inside the surface.

These polymer beads can be used as master beads alone or mixed with other polymer beads to provide a raw material for melt extrusion molding, and can provide molded products of good quality. Next, the present invention will be explained in more detail with reference to Examples.

Example l 200 kg of beads (average particle size 0.3 mm) of methyl methacrylate polymer (viscosity average molecular weight approximately 100,000) containing 3% by weight of methyl acrylate units were placed in FM5 manufactured by Mitsui Miike Seisakusho.
After charging the mixer into an OOF type pen shell mixer and thoroughly replacing the space in the mixer with nitrogen gas, the
, stirring was started at a circumferential speed of 40 m/Sec, and immediately 1.6 kg of methyl methacrylate and di-adipate n-
A premix of 2.4 kg of butyl was added in 1 minute.

Internal flow is smooth. Make sure that After confirming this, 56 kg of barium sulfate, 0.6 kg of titanium oxide, and 20 g of ultramarine blue were added in 1 minute. Continue stirring further, and after 2 minutes and 30 seconds, lower the rotation speed to 430 rpm and continue stirring for 5 minutes and 30 seconds.
During this time, the internal temperature reached 75°C. In this way,
Master beads with inorganic pigments uniformly adhered to their surfaces were obtained. Electron microscopy of the surface of this master bead 3
A 00x enlarged photograph is shown in Figure 1. For comparison, FIG. 2 shows a 300 times enlarged photograph of the surface of beads obtained by simply mechanically mixing polymer beads and inorganic filler powder according to the conventional method.

As is clear from comparing the two, the beads obtained by the present invention have a uniform and smooth surface, whereas the surfaces of the beads obtained by the conventional method are uneven and rough.

Example 2 Polymer beads were coated in the same manner as in Example 1, except that the various compound combinations shown in Table 1 were used.

The surface conditions of the beads thus obtained were all the same as those in FIG.

Example 3 The surface conditions of polymer beads obtained by the same treatment as in Example 1 except for varying the amounts of methyl methacrylate and dibutyl adipate were observed, and the results are shown in Table 2.

Reference Example The polymer beads having the surface shown in FIG. 1 obtained in Example 1 and the polymer beads having the surface shown in FIG. 2 obtained by the conventional method were mixed into polymethyl methacrylate beads 10
They were added at a ratio of 14 parts by weight to 0 parts by weight, thoroughly blended in a lipon blender, and then formed into a sheet using a 90 mm diameter extruder (L/D-26, deep groove, with kneading section, with vent).

When we observed changes in the resin pressure and required power over time, we found that the fluctuation range when using beads obtained by the method of the present invention was 1/1/2 of the fluctuation range when using beads obtained by the conventional method.
It was 2-1/3.

[Brief explanation of the drawing]

FIG. 1 is a microscopic photograph of the surface of a polymer bead obtained by the present invention, and FIG. 2 is a microscopic photograph of the surface of a polymer bead obtained by a conventional method.

Claims (1)

[Claims] 1. When coating the surface of methyl methacrylate polymer beads with an inorganic filler, (a) general formula ▲ mathematical formula, chemical formula, table, etc. for 100 parts by weight of methyl methacrylate polymer beads. 0.2 to 2.0 parts by weight of an acrylic ester or methacrylic ester represented by ▼ (in the formula, R_1 is a hydrogen atom or a methyl group, and R_2 is a lower alkyl group) and (b) general formula R_3O.
OC-(CH_2)_n-COOR_4 (R_3 in the formula
and R_4 is a lower alkyl group, and n is an integer of 4 to 8), and stirred at high speed to create a swollen state on the surface of the polymer beads. 1. A method for producing methyl methacrylate polymer beads coated with a uniform inorganic filler layer, which comprises forming, and then adding an inorganic filler powder and stirring to adhere it to the surface of the beads. 2. A method according to claim 1, wherein the proportion of inorganic filler is at most 200 parts by weight per 100 parts by weight of methyl methacrylate polymer beads.