Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-07-08
2001-09-04
Henderson, Christopher (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C260SDIG031, C524S161000
Reexamination Certificate
active
06284823
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to acrylic resin compositions which have excellent antistatic property and good appearance, with small decrease of an antistatic property particularly when using a masking film. The present invention is to provide suitable materials for electric and electronic appliances, covers for lighting apparatus, and lens for projection TVs, to which dust may often be adhered.
2. Description of Related Arts
Acrylic resins have been widely utilized in many fields such as electric appliances and household use articles in the form of sheets, molded products, etc., due to favorable characteristics such as lightness in the weight and easy handlings. Although the resins are excellent in electric insulation performance, they have some disadvantages in the charge and accumulation of static electricity. For instance, dust is easily adhered on the surface of the apparatus until the transparency and luster are degraded, the fine appearance is damaged and the commercial values are decreased. In order to cope with such problems, one of approaches is that, to acrylic resins, is added a metal salt of alkylsulfonic acid represented by the formula R—SO
3
M, wherein R is an alkyl group and M is a salt-forming metal such as alkali and alkaline earth metals. However, addition of antistatic agents encounters problems such as decrease in transparency, deterioration in appearance, etc. JP 7-18137A and 7-207088A suggest to blend a specific resin with a particular metal sulfonate salt, in order to dissolve the problems.
Furthermore, the surfaces of thermoplastic resin products are generally masked with, for example, a polyethylene film, in order to protect appearance thereof. Acrylic resin compositions prepared according to the methods mentioned above are, however, not free from disadvantages in remarkable decrease of antistaticity, after a long time contact with the masking film. This would be probably due to migration of the antistatic agent applied on the surface of the compositions to a paste of the masking film. If the paste for masking film is replaced by that which the antistatic agent hardly migrates to, peeling-off of the masking film tends to occur, causing difficulties in maintenance and storage.
SUMMARY OF THE INVENTION
After the present inventors have made extensive studies to overcome the drawbacks in the conventional methods, they succeed in producing acrylic resin compositions which can be preserved and stored for a long period of time with an excellent adhesiveness to resin materials for masking, by blending an acrylic resin with specific phosphonium sulfonate and lithium sulfonate, each in specific amounts and with specific amount ratio, as well as fatty acid ester and/or fatty acid amide. Namely, the present invention is an acrylic resin composition which comprises (A) 100 parts by weight of an acrylic resin; (B) a phosphonium sulfonate represented by the formula I:
wherein R
1
is a straight-chain or branched long-chain alkyl or alkenyl group having 8 to 22 carbon atoms and R
2
through R
5
are, respectively, a hydrogen atom or alkyl or aryl group having 1 to 10 carbon atoms, which may be the same or different; (C) a lithium sulfonate of the formula II:
wherein R
1
has the same meaning as above, the weight ratio of (B)/(C) being within the range from 2/8 to 8/2 and the total amount of (B) and (C) being 0.2 to 2.5 parts by weight; and (D) 0.05 to 2.0 parts by weight of a fatty acid ester and/or fatty acid amide.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be further described hereunder. The acrylic resins (A) of this invention include homopolymers or copolymers of acrylic acid, acrylic acid esters, methacrylic acid and methacrylic acid esters. The acrylic resins (A) employed in the invention are those having not less than 50% by weight of methyl methacrylate monomer unit. Preferably, they are methyl methacrylate-styrene copolymer resins having methyl methacrylate unit to styrene unit of from 80:20 to 50:50 by weight. More preferably, from the view points of kneaded extrusion and the physical properties, those having 100,000 to 200,000 of weight average molecular weight, being readily extrusion-moldable at a temperature of 250° C. or less, and having 1.50 to 1.54 of an index of refraction are suitable for various optical instruments. If the temperature at the extrusion exceeds 250° C., the antistatic agent isolated causes whiting and the like to damage appearance.
The acrylic resins (A) are produced according to any of known polymerization methods, such as bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization, melt polymerization, and the like. Forms of the resins may be of pellets, beads, powdered or pulverized amorphous matters, or molten state, so far as they can be dealt with extruders.
The phosphonium sulfonates (B) are represented by the formula I:
wherein R
1
is a straight chain or branched long-chain alkyl or alkenyl group having 8 to 22 carbon atoms, and R
2
through R
5
are, respectively, a hydrogen atom or alkyl or aryl group having 1 to 10 carbon atoms, which may be the same or different.
The phosphonium sulfonates (B) are composed of organic sulfonate anions and organic phosphonium cations. As such organic sulfonate anions, there are mentioned octylbenzenesulfonate, decylbenzenesulfonate, dodecylbenzenesulfonate, tetradecylbenzenesulfonate, hexadecylbenzenesulfonate, octadecylbenzenesulfonate, and the like, which may be used singly or as a mixture.
As the organic phosphonium cations, there are mentioned tetramethylphosphonium, tetraethylphosphonium, tetrabutylphosphonium, triethylmethylphosphonium, tributylmethylphosphonium, trioctylmethylphosphonium, trimethylbutylphosphonium, trimethyloctylphosphonium, trimethyllaurylphosphonium, trimethylstearylphosphonium, triethyloctylphosphonium, tributyloctylphoshonium and the like aliphatic phosphonium cations; triphenylmethylphosphonium, triphenylethylphosphonium and the like aromatic phosphonium cations; and triphenylbenzylphosphonium, tributylbenzylphosphonium and the like alkylarylphosphonium cations. Further, tetramethylolphosphonium, tri(2-cyanoethyl)methylphosphonium, tri(2-cyanoethyl) ethylphosphonium, tri(2-cyanoethyl)benzylphosphonium, tri(3-hydroxypropyl)benzylphosphonium, trimethyl-(2-hydroxyethyl)phosphonium, tributyl(2-hydroxyethyl) phosphonium and the like substituted aliphatic phosphonium cations may also be used.
Among these phosphonium sulfonates, tetrabutylphosphonium dodecylbenzenesulfonate and tetrabutylphosphonium 1,6,8-trimethylnonylbenzene sulfonate are preferable. Thus the phosphonium sulfonates according to the present invention may be composed of such organic sulfonate anions and such organic phosphonium cations, as exemplified, in arbitrary combinations, but they should not be limited thereto.
The lithium sulfonates (C) are represented by the formula II:
wherein R
1
has the same meaning as above. As the specific examples of the lithium sulfonates, there are mentioned, for example, lithium octylbenzenesulfonate, lithium dodecylbenzenesulfonate, lithium triisopropylnaphthalenesulfonate, lithium dibutylnaphthalenesulfonate and the like, but they should not be limited thereto. Among those lithium compounds of the formula II as illustrated above, lithium dodecylbenzenesulfonate is preferable.
The lithium sulfonates (C) are highly hygroscopic. Those in solution form are preferable, because those in the solid state are so readily coagulated and sticky, that they are too difficult to handle. The solution can be prepared by mixing the lithium sulfonate (C) with a solvent under stirring at room temperature. Any of solvents may be used so far as it has diffusibility and dissolves the lithium sulfonates (C). Water, methanol, ethanol, isopropanol and other lower alcohols, as well as mixtures thereof, may be used. Preference is mixtures of water with methanol or isopropanol, because they give large solubility and are easily handled. A concentration of the lithium sulfo
Kokuzawa Yukio
Sato Kazunobu
Fitch Even Tabin & Flannery
Henderson Christopher
Mitsubishi Gas Chemical Company Inc.
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