Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2001-04-06
2003-03-04
Dawson, Robert (Department: 1712)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C427S394000, C427S395000, C428S447000, C428S452000, C162S135000, C162S164400, C524S731000, C524S837000, C524S838000, C524S860000, C524S863000, C524S869000, C528S015000, C528S017000, C528S026000, C528S026500, C528S027000, C528S032000, C528S033000, C528S038000, C528S041000
Reexamination Certificate
active
06528121
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an aqueous treatment agent for wiping paper, and more particularly to an aqueous treatment agent for wiping paper capable of rendering tissue paper, toilet paper, and other types of wiping paper dry to the touch, highly smooth, nonsticky, and extremely soft while suppressing the slippery or wet feel thereof.
BACKGROUND OF THE INVENTION
Tissue paper, toilet paper, and other types of wiping paper are disadvantageous in that they lack adequate softness or smoothness as such, and thus cause skin roughness/redness or pain when used frequently.
Examples of methods proposed to address this problem include methods in which these types of wiping paper are treated with a polydimethylsiloxane having hydrogen bond functional groups selected from among amino groups, carboxyl groups, hydroxyl groups, ether groups, polyether groups, aldehyde groups, ketone groups, amido groups, ester groups, and thiol groups (see Japanese Patent Applications Kokai 2-224626 and 3-900); methods of treatment with water dispersions of polyether group-containing polydiorganosiloxanes and amino group-containing polydiorganosiloxanes (see Japanese Patent Application 6-311943); and methods of treatment with polydiorganosiloxanes and polyhydric alcohols (see Japanese Patent Application 7-145596).
Wiping paper treated with these polydiorganosiloxanes is still disadvantageous because it lacks softness and still has a rough feel and an inadequate hand. A particular drawback is that a treatment performed using a polydiorganosiloxane containing amino groups results in an excessively slippery product with poor tactile attributes. A treatment performed using a polydiorganosiloxane containing polyether groups is disadvantageous in that it fails to produce adequate smoothness (slip).
An object of this invention is to provide an aqueous treatment agent for wiping paper capable of rendering tissue paper, toilet paper, and other types of wiping paper dry to the touch, highly smooth, nonsticky, and extremely soft while suppressing the slippery or wet feel thereof.
SUMMARY OF THE INVENTION
The aqueous treatment agent for wiping paper comprises a water dispersion of a silicone rubber powder with an average particle diameter of 0.1 to 500 &mgr;m.
DETAILED DESCRIPTION OF THE INVENTION
A distinctive feature of the present treatment agent is that it consists of a water dispersion of silicone rubber powder. Such a silicone rubber powder is a component designed to render wiping paper dry to the touch, highly smooth, nonsticky, and extremely soft while suppressing the slippery or wet feel thereof. The average particle diameter of the silicone rubber powder should fall within a range of 0.1 to 500 micrometers, preferably 0.1 to 100 micrometers, and ideally 0.5 to 50 micrometers. This is because a treatment agent containing a silicone rubber powder whose average particle diameter falls outside this range tends to become incapable of rendering wiping paper dry to the touch, highly smooth, nonsticky, and extremely soft while suppressing the slippery or wet feel thereof. The silicone rubber powder may be shaped as spherical, flat, or irregular particles, with spherical particles being particularly preferred. The silicone rubber powder should have a hardness (measured as type A durometer hardness in accordance with JIS K 6253) of 80 or lower, and preferably 65 or lower. This is because a treatment agent containing a silicone rubber powder whose hardness falls outside this range tends to be less likely to render wiping paper dry to the touch, highly smooth, nonsticky, and extremely soft while suppressing the slippery or wet feel thereof.
The treatment agent can be prepared by dispersing the silicone rubber powder in water, although a preparation procedure in which a silicone rubber composition is cured in advance as a dispersion in water is preferred because the silicone rubber powder as such tends to aggregate easily and is difficult to uniformly disperse in water when this silicone rubber powder has low hardness.
Methods in which a hydrosilylation reaction-curing silicone rubber composition, condensation reaction-curing silicone rubber composition, organic peroxide-curing silicone rubber composition, ultraviolet-curing silicone rubber composition, or other silicone rubber composition is cured while dispersed in water are examples of the method for preparing a water dispersion of silicone rubber powder by curing a silicone rubber composition as a dispersion in water. It is particularly suitable to use a method in which a hydrosilylation reaction-curing silicone rubber composition or a condensation reaction-curing silicone rubber composition is cured while dispersed in water with the aid of a surfactant.
Examples of hydrosilylation reaction-curing silicone rubber compositions include those comprising at least a polyorganosiloxane having two or more alkenyl groups per molecule, a polyorganosiloxane having two or more silicon-bonded hydrogen atoms per molecule, and a platinum-based catalyst.
Examples of condensation reaction-curing silicone rubber compositions include those comprising at least a polyorganosiloxane in which each atom has two or more hydrolyzable groups such as aminoxy groups, acetoxy groups, oxime groups, and alkoxy groups or hydroxyl groups bonded to silicon atoms; a silane-based cross-linking agent in which each atom has three or more hydrolyzable groups such as aminoxy groups, acetoxy groups, oxime groups, and alkoxy groups bonded to silicon atoms; and a condensation reaction catalyst such as an organotin compound or organotitanium compound.
Another distinctive feature of this invention is that a silicone rubber powder containing an uncross-linked silicone oil may be used as the silicone rubber powder, in which case the resulting treatment agent is even more effective in rendering wiping paper dry to the touch, highly smooth, nonsticky, and extremely soft while suppressing the slippery or wet feel thereof.
Examples of methods for preparing such a silicone rubber powder include methods in which a silicone oil that does not contribute to the curing reaction of a silicone rubber composition is premixed with the composition, which is then cured in powder form; and methods in which the silicone rubber powder is impregnated with silicone oil. The second group of methods is more preferred.
The uncross-linked silicone oil is an oil that can be merely added to a silicone rubber powder and then be allowed to naturally leak from the powder or be extracted with an organic solvent. Such a silicone oil may, for example, have a straight, cyclic, or branched molecular structure. A straight structure is preferred. Examples of such silicone oils include trimethylsiloxy-endblocked polydimethylsiloxanes, trimethylsiloxy-endblocked dimethylsiloxane/methylphenylsiloxane copolymers, trimethylsiloxy-endblocked dimethylsiloxane/methyl(3,3,3-trifluoropropyl)siloxane copolymers, and other unreactive silicone oils.
The following compounds are cited in addition to the aforementioned nonreactive silicone oils when these silicone oils are contained in advance in the silicone rubber composition for forming the silicone rubber powder: trimethylsiloxy-endblocked polydimethylsiloxanes that do not contribute to such curing reactions; polyorganosiloxanes obtained by substituting some of the methyl groups of these polydimethylsiloxanes with 3,3,3-trifluoropropyl groups, phenyl groups, or alkyl groups other than the methyl group; and other such silicone oils.
The following compounds may be cited in addition to the aforementioned nonreactive silicone oils when the curing reaction is an addition reaction: silanol-endblocked polydimethylsiloxanes; polyorganosiloxanes obtained by substituting some of the methyl groups of these polydimethylsiloxanes with 3,3,3-trifluoropropyl groups, phenyl groups, or alkyl groups other than the methyl group; and other such silicone oils. Additional examples include silicone oils that remain unreacted despite being capable of contributing to this curing reaction, such as dimethylvinylsilox
Kobayashi Kazuo
Morita Yoshitsugu
Ona Isao
Ozaki Masaru
Brown Catherine U.
Dawson Robert
Dow Corning Toray Silicone Co. Ltd.
Gobrogge Roger E.
Richard Charles
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