Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-02-13
2003-01-07
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S232000, C525S241000
Reexamination Certificate
active
06503987
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a modifier composition for methacrylate resin, which is used for a thermoplastic resin particularly for a methacrylate resin and can stably give an molding article having an excellent strength (impact resistance) without deteriorating transparency, color tone and appearance thereof under a wide range of injection molding conditions.
BACKGROUND ART
A methacrylate resin has been used in lighting devices and outdoor article due to its high transparency and good weatherability. On the other hand, its strength is not necessarily sufficient, and thus various kinds of impact modifiers have been attempted to be added thereto. For example, Japanese Examined Patent Publication Nos. 55-27576 (1980) and 62-230841 (1987) disclosed modifying technique relating thereto. It is necessary not to lose transparency, color tone and appearance of a methacrylate resin under a wide range of processing conditions. However, when the techniques previously disclosed are used in processing a methacrylate resin, it is difficult to satisfy the requirement that a methacrylate resin excellent in strength is stably obtained without deteriorating transparency, color tone and appearance thereof under a wide range of processing conditions. In fact, a transparent molded articles can be obtained under limited processing conditions, and an appearance thereof becomes worse due to agglomeration of the impact modifier during processing. Namely, if a molding temperature is raised in order to obtain a molded article having high transparency, the article is thermally deteriorated, color tone thereof becomes lower, and a resin gets yellowish under a slight fluctuation in processing conditions. On the other hand, if the injection molding temperature is set low, appearance of the article becomes worse so that transparency thereof is deteriorated significantly.
As a measure for these problems, some investigations have been carried out in order to stably obtain a molded article having high physical properties. For example, there are disclosed a method for using a methacrylate resin having a broad distribution of molecular weight to improve fluidity and the balance between strength and fluidity (Japanese Examined Patent Publication No. 1-29218 (1989)), and a technique for mixing an impact modifier with a dispersing agent in the state of latex to prevent agglomeration of the impact modifier as a means for reducing the so-called fish eye on the surface of an injection molding (Japanese Examined Patent Publication No. 2-2358 (1990)). However, these were not sufficient from the viewpoint that a molded article having excellent strength is obtained without deteriorating transparency, color tone and appearance thereof under a wide range of injection molding conditions in the present invention.
In the present invention there is provided a modifier composition for a methacrylate resin, which can stably give a molded article excellent in strength without deteriorating transparency, color tone and appearance thereof under a wide range of injection molding conditions.
DISCLOSURE OF INVENTION
In view of these circumstances, the present inventors extensively studied a resin composition having an excellent strength without deteriorating characteristics of a methacrylate resin, namely, transparency, color tone and appearance under a wide range of injection molding conditions. As a result, it was found out that the above problems in injection molding can be solved by blending an impact modifier, a polymer processing aid and a reducing compound with a methacrylate resin to complete the present invention.
Namely, the present invention relates to
(1) a modifier composition for a methacrylate resin comprising an impact modifier, a polymer processing aid and a reducing compound, wherein a ratio of the impact modifier to the polymer processing aid is 95/5 to 80/20 in weight, and an amount of the reducing compound is 0.25 to 1.25 parts by weight based on 100 parts by weight of the total amount of the impact modifier and the processing aid,
(2) the modifier composition for a methacrylate resin of the above (1), wherein the impact modifier is obtained by polymerizing a monomer mixture comprising (meth)acrylate and an aromatic vinyl monomer in the presence of an acrylic rubber and/or a conjugated diene rubber,
(3) the modifier composition for a methacrylate resin of the above (1) or (2), wherein the polymer processing aid comprising 50 to 70% by weight of methyl methacrylate and 30 to 50% by weight of the other monomer copolymerizable therewith,
(4) the modifier composition for a methacrylate resin of the above (1), (2) or (3), wherein a specific viscosity of the polymer processing aid is 2.5 to 5.0 regarding to 0.4% by weight of a toluene solution at 30° C.,
(5) the modifier composition for a methacrylate resin of the above (1), (2), (3) or (4), wherein the reducing compound is a compound containing sulfur and/or phosphorus, and
(6) the modifier composition for a methacrylate resin of the above (5),
wherein the reducing compound is an organic reducing compound.
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention there is no particular limitation for a methacrylate resin, it includes a resin containing at least 50% by weight of methacrylate unit, preferably at least 50% by weight of methyl methacrylate unit, and any commercially available methyl methacrylate resins can be used.
There is no particular limitation for an impact modifier used in the present invention, as long as it can be used in a methacrylate resin. In particular, the modifier is preferable which is prepared by polymerizing a monomer mixture comprising (meth)acrylate and an aromatic vinyl monomer, to which another copolymerizable monomer may be added depending on the object, in the presence of an acrylic rubber and/or a conjugated diene rubber. Since these are well-compatible with a methacrylate resin to significantly improve impact strength thereof As these modifiers, there are known those having various kinds of multilayer structure, and, for example, those disclosed in Japanese Examined Patent Publication No. 55-27576 (1980) can also be used. Further, the polymerization method is not particularly limited, but the known emulsion polymerization method is practically convenient. However, if only the impact modifier is added to a methacrylate resin, there arises the problem that transparency, color tone and appearance inherent in a methacrylate resin are deteriorated depending on processing conditions.
As a conjugated diene rubber, examples are those rubbers comprising diene monomers such as butadiene, isoprene and chloroprene. As an acrylic rubber, examples are alkyl acrylates having 1 to 12 carbon atoms in the alkyl group, such as ethyl acrylate, n-butyl acrylate, n-octyl acrylate and 2-ethylhexyl acrylate. Examples of an aromatic vinyl monomer are styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, &agr;-methylstyrene and chlorostyrene. Examples of a (meth)acrylate are methyl acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate, hexyl(meth)acrylate, cyclohexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, octyl(meth)acrylate, isobomyl(meth)acrylate, phenyl(meth)acrylate and benzyl(meth)acrylate, and the like.
The polymer processing aid used in the present invention should have a relatively high molecular weight, and it is effective to use the modifier having a several to tens times higher molecular weight than that of a generally used methacrylate resin (weight average molecular weight is about 100,000). That is, apart from the generally conceivable technical idea in the prior art, the addition of a small amount of the polymer processing aid reduces the dependence of transparency on processing conditions, although the viscosity in the system rises slightly. The technical reason speculated for this is that the melting elasticity in the system becomes high to improve inferior appearance and stabilize transparency. Further, an amount of the polymer processing aid in the present invention is preferably 5
Kitayama Fuminobu
Nagata Norio
Sugaya Takahiko
Takaki Akira
Armstrong Westerman & Hattori, LLP
Kaneka Corporation
Nutter Nathan M.
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