KR100274658B1 - A preparing method of core-shell composite particles for toughening agent of polymethyl methacrylate resin and composition containing the same - Google Patents

Abstract

PURPOSE: A method for preparing core-shell composite particles for impact-reinforcing agent containing polymethyl methacrylate is provided to utilize the particles to control the refraction index of the core and obtain the high transparency and improved impact-resistance. CONSTITUTION: The method for preparing core-shell composite particles for impact-reinforcing agent containing polymethyl methacrylate comprises the first step of forming seed latex by polymerizing 15-25 wt.% of the reactant material comprising 97.0-99.5 wt.% of the mixture of butyl acrylate and styrene monomer in a weight ratio of 8:2 and 0.5-3 wt.% of divinylbenzene; the second step of preparing core-shell latex by reacting 100 weight parts of the core latex and 50-100 weight parts of the methylmethacrylate; and the third step of agitating the core-shell latex at 70-90 deg.C in the presence of magnesium sulfate and drying it at 40-60 deg.C. The particles has average particle diameter of 200nm or less. The divinylbenzene is used as the cross-linking agent and the controlling agent of refraction index.

Description

[Name of invention]

Method for preparing core-cell composite particles for impact modifier of polymethyl methacrylate and product containing same

Detailed description of the invention

[Purpose of invention]

[Technical field to which the invention belongs and the prior art in that field]

The present invention relates to a method for preparing a core-shell composite particle for impact modifier of polymethyl methacrylate and a composition containing the same, and more particularly, to a high transparency and impact polymethyl methacrylate resin by controlling the refractive index of the core The present invention relates to a method for producing a core-shell composite particle suitable as an impact modifier and a product containing the same.

Polymethyl methacrylate resin has excellent surface appearance, relatively high glass transition temperature and excellent mechanical properties in addition to excellent transparency that transmits about 95% of visible light, such as glass substitutes, electronic components and building materials. It is widely used as a molding material. In addition, chemical resistance, excellent weather resistance and water repellency is widely used in the field of paints and adhesives. However, polymethyl methacrylate resins have impact strengths as low as 1/6 to 1/7 compared to ABS (acrylonitrile-butadiene-styrene) resins or ASA (acrylonitrile-styrene-acrylonitrile) resins. Because of this, there are many restrictions on its use. Moreover, there is a drawback that the transparency is lowered because of the low surface strength and fragility, which tends to cause surface wear and scratches. Therefore, research to develop a polymethyl methacrylate resin having high impact resistance and at the same time can maintain high transparency is continuing.

Generally, a method of reinforcing glassy plastic having a low impact strength is a method of copolymerizing a polymer having a low glass transition temperature and a glassy plastic together, a blending method which is physically dispersed in a plastic to strengthen the rubbery polymer, and a rubbery polymer and The method of disperse | distributing the core-cell composite particle which consists of glassy polymer continuously in a glassy polymer matrix, etc. is known. When the polymethyl methacrylate resin is strengthened by double copolymerization, there is no problem in transparency, but the physical properties at the time of reinforcement are significantly influenced by the properties of the comonomer, so that the surface strength and other mechanical properties are significantly lowered. When blending a polymer with a polymethyl methacrylate resin, the impact resistance may be improved to a certain extent, but the transparency loss due to the phase separation of rubbery materials is increased, and thus high transparency, which is one of the excellent physical properties of the polymethyl methacrylate resin, is high. It is hard to expect. In addition, butadiene alone or a copolymer of styrene and butyl acrylate and a general crosslinking agent (for example, ethylene glycol dimethacrylate, triglycol dimethacrylate, or In case of reinforcing polymethyl methacrylate resin by synthesizing the core with only aryl methacrylate), the final physical properties of the material such as the transparency decreases significantly because the refractive index of the core portion is different from that of polymethyl methacrylate, which is a matrix resin. This situation is reported to adversely affect.

In this regard, British Patent No. 1,414,187 and U.S. Patent No. 4,543,383 solve the problem of transparency caused by impact strengthening by using composite particles having a three-layer structure as impact modifier of polymethyl methacrylate having low impact strength. The technique is disclosed. However, when the multi-layered composite particles are used as impact modifiers of the polymethyl methacrylate, the manufacturing process of the composite particles becomes quite complicated, causing problems in efficiency.

In general, most rubbery polymers have a significantly lower refractive index than glassy matrices. For this reason, in the impact resistance of polymethyl methacrylate using composite particles, if only the rubbery portion of the polymer having rubbery properties is used, the original transparency cannot be maintained after the impact resistance. The monomer which has is copolymerized with a rubbery component. However, since monomers such as styrene having a high refractive index during polymerization are often glassy polymers, when a large amount is used to control the refractive index, there is a problem in strengthening the impact resistance.

[Technical problem to be achieved]

Accordingly, in the present invention, in order to solve the above-mentioned problems, the refractive index is adjusted by using a divinylbenzel which exhibits a high refractive index when polymerizing a rubber core having a low refractive index as a crosslinking agent and polymerizing the amount of the divinylbenzene. By matching the refractive index of the core part with the refractive index of the cell part, the impact-resistant polymethyl methacrylate produced can be made impact resistant while maintaining the high transparency possessed by the original polymethyl methacrylate.

Accordingly, an object of the present invention is to provide a method for producing core-cell composite particles having improved transparency of polymethyl methacrylate by adjusting the refractive index of polymethyl methacrylate resin as an impact modifier.

Another object of the present invention is to provide a product containing the core-cell composite particles produced by the above method.

Method for producing a core-cell composite particles according to the present invention for achieving the above object is emulsified 97 to 99.5% by weight of copolymer of butyl acrylate and styrene and 0.5 to 3% by weight of divinylbenzene in the presence of a solvent and a polymerization initiator Polymerizing to form a core; Preparing a core-cell latex by adding methyl methacrylate to the core in a weight ratio of 1: 1; And stirring the core-cell latex at 70-90 ° C. in the presence of magnesium sulfate and then drying at 40-60 ° C.

The product of the present invention for achieving the above another object is prepared by melting and mixing 15 to 30% by weight of the core-cell composite particles prepared by the above method and 70 to 85% by weight of the polymer resin having a low impact strength of high transparency.

[Configuration and Function of Invention]

Looking at the present invention in more detail as follows.

A cross-section of a core-cell composite particle according to the present invention is schematically illustrated in FIG. In FIG. 1, the cell portion is made of a high transparency, low impact polymer resin such as polymethyl methacrylate resin, and the core portion is a monomer, which forms a rubbery phase during polymerization, such as mutyacrylate, divinylbenzene, and styrene. The copolymerized polymer of the monomer which shows high refractive index at the time of superposition | polymerization like this is used.

In the present invention, in order to control the refractive index of the core-cell composite particles by using a crosslinking agent and divinyl benzene having a very high refractive index at the time of polymerization, the composite particles with improved refractive index of the core portion are prepared to maintain the transparency of the polymethyl methacrylate. Impact resistance could be improved.

In the present invention, the core-cell composite particles were prepared using two-step continuous emulsion polymerization. In general, the preparation of such core-cell composite particles consists of three stages: seed latex polymerization, core latex polymerization, and cell polymerization. In the polymerization of the core in the preparation of the composite particles, some of the components constituting the core are first polymerized to prepare seed latex, and then seed emulsion polymerization is used to polymerize the rest. This is because the rubber latex has a uniform particle size, and as a result, the core-cell composite particles as shown in FIG. 1 are easy to have a uniform particle size.

In seed latex polymerization, a portion of the mixture of 97 to 99.5 wt% butyl acrylate, styrene and 0.5 to 3 wt% divinylbenzene (about 15 to 25 wt%) is reacted in the presence of a solvent and a polymerization initiator to form a seed. Let's do it. In the core latex polymerization, the remaining mixture is added dropwise to the reactant at a rate of 20-25 g / mim to prepare a core latex. In cell polymerization, methyl methacrylate having the same weight as the core is added dropwise to the core at a rate of 20 to 25 g / mim. The core-cell latex thus prepared is stirred at about 70-90 ° C. in the presence of magnesium sulfate (latex flocculant), and then dried at about 40-60 ° C. to prepare core-cell composite particles. At this time, the mixing ratio of the butyl acrylate and styrene is preferably 8: 2, if outside the range there is a great difficulty in maintaining the refractive index and the elasticity of the core. In addition, when the amount of the divinyl benzene is less than 0.5% by weight, the refractive index is slightly lower than that of polymethyl methacrylate, and when the amount of the divinyl benzene is more than 3% by weight, the degree of crosslinking of the core is increased to decrease elasticity. On the other hand, the amount of the methyl methacrylate is preferably added in an amount of 50 to 100 parts by weight based on 100 parts by weight of the mixture of the monomer, if less than 50 parts by weight can be obtained inverted core-cell latex, 100 Exceeding parts by weight may result in the formation of polymethylmethacrylate homo latex. In addition, the stability of the latex is lowered outside the addition rate.

In addition, when polymerizing the cell with the rest of the core (75-85% by weight), a semi-batch continuous process was used to suppress the formation of new particles and to form the core-cell multiparticulate structure well.

The present invention is characterized in that divinylbenzene is used as a crosslinking agent for controlling the refractive index and core in the core latex polymerization. As described above, in general, the refractive index of the rubbery polymer is considerably lower than the refractive index of the glassy polymer, and in order to solve this problem, copolymerizing the glassy polymer of high refractive index with the rubbery polymer loses its properties. Therefore, this problem has been solved by using divinylbenzene, which exhibits a high refractive index upon polymerization, as a crosslinking agent while maintaining the properties of the rubbery core.

The core-cell composite particles thus prepared are melt-mixed with a high transparency, low impact polymer resin such as polymethyl methacrylate. The mixing ratio is preferably 70 to 85% by weight of polymethyl methacrylate and 15 to 30% by weight of the core-cell composite particles. If the core-cell composite particles are less than 15% by weight, the impact resistance is insignificant, and exceeds 30% by weight. The problem arises due to the increase in viscosity and the generation of large amounts of bubbles. On the other hand, the method of the present invention can also be applied to the impact modifier of the epoxy resin used as a sealing agent for electronic components by adjusting the amount of divinylbenzene. In addition to the epoxy resin, it can be applied to all resins requiring transparency and impact resistance.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the scope of the present invention is not limited to the following Examples.

Example 1

Core-Cell Multiparticle Manufacturing

Seed latex polymerization is carried out at a stirring speed of 300 rpm to a temperature of 70 ℃. First, 38 kg of ultrapure water is added and nitrogen is blown in. When the temperature reaches 70 ° C, an aqueous solution of 25 g of potassium persulfate, a water-soluble polymerization initiator, is added to a small amount of water. Meanwhile, butyl acrylate, styrene, and divinylbenzene monomers forming the core are respectively mixed with 3.98 kg, 995 g, and 25 g, respectively, and 500 g of sigma aerosol-OT, which is an emulsifier, is stirred for 1 hour. 20 wt% of the monomer-emulsifier mixture thus prepared is first added to an aqueous solution containing the polymerization initiator to react to initiate seed latex polymerization. After 1 hour after completion of the seed latex polymerization, the remaining 80 wt% of the monomer-emulsifier mixture is added dropwise at a rate of 22.3 g / min. After 4 hours, the core latex polymerization is completed. Next, in cell polymerization, an aqueous solution of 25 g of potassium persulfate dissolved in a small amount of water is added to the reactor, and then 5 kg of methyl methacrylate monomer is added dropwise at a rate of 22.3 g / min as in core polymerization. After the injection of the methyl methacrylate monomer, the reaction is completed for 4 hours to complete the core-cell latex polymerization.

In order to obtain a core-cell composite particle by deemulsifying the core-cell latex thus prepared, first, the prepared core-cell latex is added to an aqueous 1% magnesium sulfate solution and stirred at 80 ° C. for about 1 hour. The deemulsified core-cell latex is filtered and dried at 50 ° C. for 48 hours to obtain core-cell multiparticulates.

Example 2

Core-Cell Multiparticle Manufacturing

The polymerization was carried out in the same manner as in Example 1 except that the amounts of butyl acrylate, styrene, and divinylbenzene in the compounds added during the core latex polymerization were 3.96 kg, 990 g, and 50 g, respectively.

Example 3

Core-Cell Multiparticle Manufacturing

The polymerization was carried out in the same manner as in Example 1 except that the amounts of butyl acrylate, styrene, and divinylbenzene in the compounds added during the core latex polymerization were 3.94 kg, 985 g, and 75 g, respectively.

Example 4

Core-Cell Multiparticle Manufacturing

The polymerization was carried out in the same manner as in Example 1 except that the amounts of butyl acrylate, styrene, and divinylbenzene in the compounds added during the core latex polymerization were 3.92 kg, 980 g, and 100 g, respectively.

Example 5

Core-Cell Multiparticle Manufacturing

The polymerization was carried out in the same manner as in Example 1 except that the amount of butyl acrylate, styrene and divinylbenzene in the compound added during the core latex polymerization was 3.88 kg, 970 g, and 150 g, respectively.

On the other hand, the particle size and particle size distribution of the core latex and core-cell latex prepared in Examples 1 to 5 was measured by laser light scattering (laser light scattering), the result of the particle size of the core and core-cell latex Is shown in Table 1 below.

As can be seen from Table 1, the particle size of the core latex was about 179 ~ 188 nm as the divinylbenzene increases. The particle size distribution of the prepared core shows a narrow particle size distribution. It can be seen that divinylbenzene hardly affects the particle size and particle size distribution of the core latex. The particle size of the core-cell latex is about 211-220 nm, and the particle size distribution shows a narrow distribution similar to that of the core latex. Therefore, in the present invention, the core-cell composite particles having a narrow particle size distribution can be produced without being affected by the divinylbenzene of the core.

In addition, the refractive indices of the core latexes prepared in Examples 1 to 5 were calculated by a Gladstone-Dale relation represented by Equation 1 below.

Here, n _i and v _i represent the refractive index and the volume fraction of each component.

On the other hand, the components used in the core latex polymerization is the refractive index when the polymerization is polybutyl acrylate 1.463, polystyrene 1.59, polydivinylbenzene 1.615 and polymethyl methacrylate 1.4893, using the above relationship in Examples 1 to 5 The prepared core latex refractive index is shown in Table 2 below.

As can be seen in Table 2, by changing the content of the divinylbenzene it is possible to greatly control the refractive index of the core of the core cell shell particles, in particular the content of the divinylbenzene prepared in Example 2 is 1wt% It can be seen that the refractive index of the core of the core cell composite particle is most similar to that of pure polymethylmethacrylate.

Comparative Example 1

10 kg of pure polymethyl methacrylate chip was melt blended at 250 ° C. and 100 rpm for 7 minutes, and then the mixture was molded at 260 ° C. to prepare specimens for impact test and 3-point bending test. The specimen prepared in this Preparation Example was prepared for comparison with the specimen prepared in Examples 6 to 12 below. Specimens for impact testing followed the Unnotch Izod type of ASTM D256 specifications, and specimens for the 3-point bending test followed the ASTM D790M specifications.

Example 6

2 kg of the core-cell composite particles prepared in Example 1 and 8 kg of pure polymethyl methacrylate chip were melt blended at 250 ° C. and 100 rpm for 7 minutes, and then the mixture was molded at 260 ° C. to provide impact resistance and 3- A specimen for point bending test was produced. Specimens for impact testing followed the Unnotch Izod type of ASTM D256 specifications, and specimens for the 3-point bending test followed the ASTM D790M specifications.

Example 7

Melt blending 1 kg of the core-cell composite particles prepared in Example 2 and 9 kg of pure polymethyl methacrylate chip at 25 p ° C. and 100 rpm for 7 minutes and then molding the mixture at 260 ° C. A specimen for point bending test was produced. Specimens for impact testing followed the Unnotch Izod type of ASTM D256 specifications, and specimens for the 3-point bending test followed the ASTM D790M specifications.

Example 8

2 kg of the core-cell composite particles prepared in Example 2 and 8 kg of pure polymethyl methacrylate chip were melt blended at 250 ° C. and 100 rpm for 7 minutes, and then the mixture was molded at 260 ° C. to give impact resistance and 3- A specimen for point bending test was produced. Specimens for impact testing followed the Unnotch Izod type of ASTM D256 specifications, and specimens for the 3-point bending test followed the ASTM D790M specifications.

Example 9

3 kg of the core-cell composite particles prepared in Example 2 and 7 kg of pure polymethyl methacrylate chip were melt blended at 250 ° C. and 100 rpm for 7 minutes, and then the mixture was molded at 260 ° C. to provide impact resistance and 3- A specimen for point bending test was produced. Specimens for impact testing followed the Unnotch Izod type of ASTM D256 specifications, and specimens for the 3-point bending test followed the ASTM D790M specifications.

Example 10

2 kg of the core-cell composite particles prepared in Example 3 and 8 kg of pure polymethyl methacrylate chips were melt blended at 250 ° C. and 100 rpm for 7 minutes, and then the mixture was molded at 260 ° C. to provide impact resistance and 3- A specimen for point bending test was produced. Specimens for impact testing followed the Unnotch Izod type of ASTM D256 specifications, and specimens for the 3-point bending test followed the ASTM D790M specifications.

Example 11

2 kg of the core-cell composite particles prepared in Example 4 and 8 kg of pure polymethyl methacrylate chip were melt blended at 250 ° C. and 100 rpm for 7 minutes, and then the mixture was molded at 260 ° C. to provide impact resistance and 3- A specimen for point bending test was produced. Specimens for impact testing followed the Unnotch Izod type of ASTM D256 specifications, and specimens for the 3-point bending test followed the ASTM D790M specifications.

Example 12

2 kg of the core-cell composite particles prepared from Example 5 and 8 kg of pure polymethyl methacrylate chips were melt blended at 250 ° C. and 100 rpm for 7 minutes, and then the mixture was molded at 260 ° C. to provide impact resistance and 3- A specimen for point bending test was produced. Specimens for impact testing followed the Unnotch Izod type of ASTM D256 specifications, and specimens for the 3-point bending test followed the ASTM D790M specifications.

Experimental Example 1

Transparency was measured by using an ultraviolet spectrophotometer using the impact resistance test specimen prepared from Comparative Example 1 and Examples 6, 8 and 10 to 12. After calculating the measured absorbance through the following equation (2) to calculate the transparency of the specimen, this value is shown in Table 3 in terms of a percentage of the transparency of the pure polymethyl methacrylate prepared in Comparative Example 1.

Where T is the transparency of the specimen, P and P ₀ are the intensity of light before and after absorption and A is the measured absorbance.

As can be seen in Table 3, it can be seen that Example 8, the divinylbenzene content of the core portion of the core-cell composite particles used is 1wt% shows the best transparency. This is because the refractive index of the core of the core-cell composite particles prepared in Example 2 is most similar to that of pure polymethylmethacrylate. Therefore, in the preparation of transparent impact-resistant polymethyl methacrylate using core-cell composite particles, it can be seen that it is most important to control the refractive index of the core in order to maintain the high transparency of the original polymethyl methacrylate. .

Experimental Example 2

Impact test specimens prepared from Comparative Example 1 and Examples 6, 8 and 10 to 12 were subjected to an impact test according to the measurement method of ASTM D256 at room temperature (25 ° C). This is to determine the influence on the impact strength according to the amount of divinylbenzene used to control the refractive index of the core, the test results are shown in Table 4 below. All tests measured five specimens each and took the average value.

As can be seen from Table 4, it can be seen that the core-cell composite particles prepared according to the present invention have a great effect on impact resistance of polymethyl methacrylate. In particular, in the case of Example 6 using the core-cell composite particles having the amount of divinylbenzene in the core of 0.5 wt% and the core of the Example 8 using the core-cell composite particles having the amount of divinylbenzene in the core 1wt% Compared with Comparative Example 1, which is the case of pure polymethyl methacrylate, in which the cell composite particles are not used, it can be seen that the impact resistance is improved by about three times. However, as the amount of divinylbenzene used in the core increases, the impact resistance decreases. As the content of divinylbenzene used to control the refractive index of the core increases, the degree of crosslinking of the core portion also increases, and eventually the elastic body of the core. This is because it reduces the properties.

Experimental Example 3

Method for measuring the ASTM D790M at room temperature (25 ℃) of the three-point bending test specimen prepared from Comparative Example 1 and Examples 6,8 and 10 to 12 in order to examine the effect of reducing the elastic properties by the degree of crosslinking According to the three-point bending test, the results are shown in Table 5 below. All tests measured five specimens and took their average values.

The specimens prepared in Examples 6, 8, and 11 to 12 were significantly reduced in bending modulus compared to the pure polymethylmethacrylate specimen prepared in Comparative Example 1, but the value increased as the amount of divinylbenzene in the core portion increased. Is increasing. Similarly, the fracture elongation was higher than the pure polymethyl methacrylate specimens prepared in Examples 6, 8 and 11 to 12, but the value decreased as the amount of divinylbenzene increased. . From these results, it can be seen that as described above, increasing the amount of divinylbenzene decreases the elastic properties of the core portion.

Experimental Example 4

Impact test specimens prepared from Comparative Example 1 and Examples 7 to 9 were subjected to an impact test according to the measuring method of ASTM D256 at room temperature (25 ℃). This is to determine the impact on the impact strength according to the amount of the core-cell composite particles, the test results are shown in Table 6 below. The core-cell composite particles used in this Experimental Example used the one prepared in Example 2 in which the refractive index of the core was the most similar to that of pure polymethylmethacrylate, and all tests measured five specimens, respectively, and the average value thereof. Was taken.

As can be seen from Table 6, it can be seen that the impact strength is significantly increased as the content of the core-cell composite particles increases, which is considered to be due to an increase in the rubbery component in the polymethyl methacrylate matrix. Therefore, it can be confirmed once again that the core-cell composite particles prepared in the present invention have a great effect on impact resistance of polymethylmethacrylate.

Experimental Example 5

In order to see the impact improvement according to the increase in the rubber phase in the polymethyl methacrylate matrix shown in Experimental Example 4, the specimen for the 3-point bending test prepared from Comparative Example 1 and Examples 7 to 9 was room temperature (25 ° C.). In the three-point bending test in accordance with the ASTM D790M measurement method, the results are shown in Table 7 below. The core-cell composite particles used in this Experimental Example used the one prepared in Example 2 used in Experimental Example 4, and all the tests measured five specimens and took their average values.

As can be seen from Table 7, as the amount of the core-cell composite particles increases, the flexural modulus decreases and the fracture elongation increases. Through this, it can be seen that as the amount of the core-cell composite particles increases, the rubber component in the matrix increases, thereby improving the impact resistance. And, according to general theories, when the amount of the core-cell composite particles is used more than 30wt%, the impact strength is expected to decrease because the distance between the particles is very short.

[Effects of the Invention]

Since the present invention can produce transparent impact-resistant polymethylmethacrylate using a composite particle having a simple core-cell structure, the manufacturing cost of the composite particle can be significantly lowered. In addition, by using a monomer having a high refractive index such as divinylbenzene and having a crosslinking ability, the impact strength of a polymer that requires transparency but low impact resistance, such as polymethylmethacrylate, can be improved.

Claims (3)

In the method for preparing a core-cell composite particle for impact modifiers of resin, 97.0-99.9 wt% of butyl acrylate and styrene monomer and 0.5-3 wt% of divinylbenzene, which are mixed at a weight ratio of 8: 2 in the presence of a solvent and a polymerization initiator. Polymerizing 15 to 25 wt% of the reactants comprising% to form a seed latex, and seed emulsion polymerizing 75 to 85 wt% of the mixture on the seed latex to prepare a core latex; Preparing a core-cell latex by reacting 50 to 100 parts by weight of methyl methacrylate based on 100 parts by weight of the core latex; And stirring the core-cell latex at 70-90 ° C. in the presence of magnesium sulfate and then drying at 40-60 ° C .; The divinylbenzene is used as a crosslinking agent and a refractive index regulator of the core latex, the core-cell composite particles of the impact modifier of polymethyl methacrylate (PMMA), characterized in that the average particle diameter of the core is 200nm or less Manufacturing method. A composition prepared by melt mixing 15-30 wt% of the core-cell composite particles and 70-85 wt% of the polymethyl methacrylate resin prepared according to the method of claim 1. Molded product prepared from the composition of claim 2.

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