Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-06-01
2001-11-20
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C525S064000, C525S071000
Reexamination Certificate
active
06319966
ABSTRACT:
This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/KR99/00241 which has an International filing date of May 14, 1999, which designated the United States of America.
TECHNICAL FIELD
The present invention relates to a polymethylmethacrylate (herein after referred to as “PMMA”) resin with an impact modifier capsulated therein which possesses good transparency and high impact resistance, and to a process of preparing the same without steps for the separate addition of a PMMA resin and impact modifier to an extruder in order to improve productivity.
The present invention intends to improve the conventional impact modifier having a core-shell structure produced by two or three emulsion polymerization steps, which includes problems that the thickness of the shell layer is increased thereby degrading the impact resistance.
Also the present invention provides a process for producing a PMMA resin with an impact modifier capsulated therein having improved reinforcing properties and processibility by increasing the thickness of the shell layer without degradation of the impact resistance and having improved properties of transparency together with impact resistance by dispersing the impact reinforcement agent uniformly in the products.
DESCRIPTION OF THE RELATED ART
Typically, a PMMA resin has been compounded with an impact modifier in the production of PMMA resin products for improving impact strength and other properties. An impact modifier for the transparent acryl resin includes a methylmethacrylate-butadiene-styrene group (hereinafter referred to as “MBS group”), an acrylonitrile-butadiene-styrene group (hereinafter referred to as “ABS group”) and an acrylate group impact modifier. Particularly, the impact modifier of the MBS and ABS groups show poor physical properties due to their low weather resistance when used in the open air for a long period, and the producing process is complicated by the use of a butadiene gas. The transparency of the impact modified PMMA is lowered because of the different refractive index of the components. Furthermore, the impact modifier of the ABS group must be used more than other kinds of the impact modifiers to obtain the same reinforcing effect.
Impact modifiers having excellent resistance against the weather and good impact strength and may include, for example, an acrylic impact modifier which is prepared from (meta)acrylic monomers, vinyl monomers such as styrene derivatives and vinyl derivatives, surfactant, initiator, crosslinking agent, and grafting agent.
The acrylic impact modifier has improved impact strength because the impact is transferred to the acrylic rubber layer from the outer matrix resin and its energy is absorbed and diverted.
Furthermore, the acrylic impact modifier has advantages in that it may be produced without degradation of the transparency by designing the rubber and matrix layers so that the refractive indexes are equal. However, when the outer stress is applied to the product, the color around the stressed portion changes to white.
To prevent such problem, the Japanese Patent Publications 1980-148729, 1971-31462 and 1979-1584 proposes the process including the stages of emulsion polymerization for making the impact modifier have a core-shell structure and finally polymerizing a hard polymer having good mixing ability with the matrix resin to the outer layer. However, such process includes problems in that the amount of impact modifier should be increased because of less content of rubber therein and the thickness of the outer layer is limited because the impact strength is more weaken when the outer layer thickness is increased.
The Japanese Patent Publication 1981-96862 discloses the process using graft copolymers having an increased content of rubber component by highly crosslinking the rubber polymer. However, such a highly crosslinked polymer has a degraded impact absorbing effect due to its decreased rubber resilience and a degraded mixing property with the matrix thereby decreasing the processibility of the product.
Furthermore, when forming the impact modified PMMA sheet by using the above mentioned impact modifier according to the prior arts, many problems have arisen in that the process is complicated and productivity is decreased because the PMMA and impact modifier should be made by separate processes and be supplied to an extruders, separately.
The formed sheet product has a degraded transparency because the impact modifier is not uniformly dispersed therein. Therefore, the thickness of the sheet product is limited in obtaining the necessary transparency.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a PMMA resin with an impact modifier capsulated therein having good transparency and good impact resistance properties.
It is another object of the present invention to provide a process for manufacturing a PMMA resin with an impact modifier capsulated therein which has advantages that the process using in producing the product is simplified and the productivity is increased.
To achieve the above objects, the present invention provides a PMMA resin with an impact modifier capsulated therein which comprises a core of a glass polymer, an intermediate layer of a rubber copolymer grafted to the core and an outer layer of a glass polymer grafted to the intermediate layer. The products have a granular shape, with the amount of the core being between 5 to 20 weight %, the amount of the intermediate layer being between 10 to 70 weight % and the outer layer being 25 to 85 weight %, the intermediate of the rubber copolymer being a copolymer of at least one monomer selected from butylacrylate or butadiene and at least one monomer selected from styrene or styrene derivative, the outer layer of the glass polymer containing a chain transfer agent.
The PMMA resin with the impact modifier capsulated therein according to the present invention has in three layer structure an impact modifier of a glass polymer core and an intermediate layer of a rubber copolymer grafted to the core and an outer layer of a glass polymer(as a matrix resin) grafted to the intermediate.
Preferably, in the PMMA resin with the impact modifier capsulated therein according to the present invention, the weight % or average diameter of the outer layer is higher or larger than that of the core. As the result, when preparing transparent sheet or molding a products, there is no need to use the matrix PMMA resin thereby simplifying the molding process and increasing the productivity.
The PMMA resin with the impact modifier capsulated therein according to the present invention is characterized by including a chain transfer agent in the outer layer. The chain transfer agent acts to adjust the molecular weight and melt viscosity of the outer layer without decreasing an impact resistance thereof.
Furthermore, the PMMA resin with the impact modifier capsulated therein according to the present invention is characterized in that the intermediate layer of a rubber polymer is composed of the copolymer of at least one monomer selected from butylacrylate or butadiene and at least one monomer selected from the styrene or styrene derivatives.
According to the present invention, a process for producing a PMMA resin with the impact modifier capsulated therein which includes three emulsion polymerizing stages as following:
First emulsion polymerizing stage for preparing emulsion of a glass polymer for a core with the conversion rate of 93 to 99%, which has an average diameter of 30 to 200 nm, by inputting the composition solution of a part of the first monomers, deionized water, emulsifier, grafting agent, and crosslinker under the nitrogen atmosphere into a reactor, heating and agitating the composition solution, emulsion-polymerizing the composition by dropping a polymerization initiator when the temperature of the composition reaches 50 to 90° C., continuously polymerizing the composition dropping the remaining first monomers when seed emulsions are formed, and finally inputting the initiator
Kang Chung Suk
Lee Kap Sung
Park Sung Mo
Birch & Stewart Kolasch & Birch, LLP
Kolon Industries Inc.
Michl Paul R.
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