Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-03-10
2001-08-28
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C523S122000, C524S435000, C524S106000, C524S588000, C528S019000, C528S034000
Reexamination Certificate
active
06281284
ABSTRACT:
This invention generally relates to antibacterial, mildew resistant organopolysiloxane compositions.
BACKGROUND OF THE INVENTION
RTV silicone rubbers which have crosslinked in the presence of moisture are easy to handle and have improved weathering and electrical properties. On account of these advantages, they find use in a variety of applications, for example, as sealants for plumbing fixtures (in kitchens and bathrooms), sealing materials in building and construction fields, and adhesives in electric and electronic fields. Among others, oxime-elimination type RTV silicone rubbers are utilized in a wider variety of applications since they remain firmly bonded to various members in wet conditions and are fully weather resistant.
As the house building technology improves these years, houses become more air-tight. Moist places in such houses are good habitats for microorganisms such as bacteria and mildew (fungi). Especially, fungi often grow on RTV silicon rubber while extending their hypha into the rubber interior. The resulting mildew is difficult to wipe off and remove even with chemical agents, detracting from the outer appearance of rubber.
One effective solution is to incorporate antibacterial agents into sealing materials. Illustrative known approaches taken for silicone sealing materials from the antibacterial and safety standpoints include the addition of 2,3,5,6-tetrachloro-4-methylsulfonylpyridine. 2-(4-thiazolyl)benzimidazole and N-substituted benzimidazolyl carbamate derivatives as disclosed in JP-A 51-106158, U.S. Pat. No. 4,247,442, and JP-A 56-38348, respectively. Sealing materials containing these compounds, however, will yellow upon application of heat or exposure to UV radiation. This yellowing problem prevents the amount of such antibacterial agents added from being increased to such an extent as to be effective for controlling the growth of all species of fungi.
U.S. Pat. No. 6,008,290 discloses an organopolysiloxane composition comprising a triazolyl group-bearing mildewstat. This composition is fully mildew resistant, but insufficiently antibacterial.
Also, JP-A 7-76654 discloses the combined use of an organic mildewstat and an inorganic antibacterial agent. This combination is effective for controlling bacteria and mildew, but unsatisfactory with respect to discoloring.
In connection with the problem of colon bacterium O-157 and the recent development and marketing of antibacterial products such as floors and sanitary ware treated to be antibacterial, the sealing materials used in such products are also required to be antibacterial.
There is a strong desire to have a sealing material which is endowed with high antibacterial and mildew resistant properties without a loss of quality such as discoloration, while maintaining safety.
SUMMARY OF THE INVENTION
An object of the invention is to provide an antibacterial, mildew resistant organopolysiloxane composition which is antibacterial, mildew resistant, resistant to heat, weather inclusive of UV, and discoloration, and safe.
The inventor has found that an organopolysiloxane composition obtained by blending an organopolysiloxane of the general formula (1) or (2) to be shown below with a silane compound having at least two hydrolyzable groups each attached to a silicon atom in a molecule or a partial hydrolyzate thereof and an antibacterial agent based on a ferrous compound will fast cure at room temperature into a silicone rubber which is antibacterial, mildew resistant, resistant to heat, weather inclusive of UV, and discoloration, and safe. When a triazole group-bearing compound is additionally blended, the organopolysiloxane composition is further improved in antibacterial and mildew resistant properties.
The inventor has found that an iron (II) compound is effective for controlling bacteria and mildew (fungi), and that when an antibacterial agent based on an iron (II) compound is blended in an organopolysiloxane composition comprising an organopolysiloxane of the general formula (1) or (2) and a silane compound having at least two hydrolyzable groups in a molecule or a partial hydrolyzate thereof, there is obtained a silicone rubber of quality which is antibacterial, mildew resistant, and resistant to weather, and eliminates the discoloration and hazard problems.
Accordingly, the invention provides an antibacterial, mildew resistant organopolysiloxane composition comprising (A) 100 parts by weight of an organopolysiloxane of the following general formula (1) or (2), (B) 0.1 to 30 parts by weight of a silane compound having at least two hydrolyzable groups each attached to a silicon atom in a molecule or a partial hydrolyzate thereof, and (C) 0.1 to 20 parts by weight of an antibacterial agent based on a ferrous compound.
HO(SiR
1
2
O)
n
H (1)
R
1
is independently a substituted or unsubstituted monovalent hydrocarbon group of 1 to 10 carbon atoms, and n is an integer of at least 10.
R
1
and n are as defined above, R
2
is a substituted or unsubstituted monovalent hydrocarbon group of 1 to 10 carbon atoms, R
3
is a monovalent hydrocarbon group of 1 to 6 carbon atoms, and m is equal to 0 or 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Component (A) of the antibacterial, mildew resistant organopolysiloxane composition according to the invention is an organopolysiloxane of the following general formula (1) or (2).
HO(SiR
1
2
O)
n
H (1)
In formula (1), R
1
is independently selected from substituted or unsubstituted monovalent hydrocarbon groups of 1 to 10 carbon atoms, for example, alkyl groups such as methyl, ethyl, propyl, butyl, hexyl and octyl; cycloalkyl groups such as cyclohexyl; alkenyl groups such as vinyl, allyl, propenyl, butenyl and hexenyl; aryl groups such as phenyl and tolyl; aralkyl groups such as benzyl and phenylethyl; and substituted ones of these groups in which some of the hydrogen atoms are replaced by halogen atoms (e.g., chlorine, fluorine and bromine), such as trifluoropropyl. Methyl is most preferred. R
1
groups may be identical or different. The letter n is an integer of at least 10 and preferably such an integer that the organopolysiloxane may have a viscosity of about 25 to about 500,000 centistokes (cSt) at 25° C., and especially about 100 to 100,000 cSt at 25° C.
In formula (2), R
1
and n are as defined above. R
2
is a substituted or unsubstituted monovalent hydrocarbon group of 1 to 10 carbon atoms, examples of which are as listed above for R
1
. R
3
is a monovalent hydrocarbon group of 1 to 6 carbon atoms, examples of which are as listed above for R
1
, preferably an unsubstituted one, and more preferably an alkyl group such as methyl. The letter m is equal to 0 or 1.
Component (B) is a silane compound having at least two hydrolyzable groups, such as ketoxime, alkoxy or alkenoxy groups, each attached to a silicon atom in a molecule or a partial hydrolyzate thereof.
The preferred silane compounds used herein are ketoximesilanes and alkoxysilanes. Most preferred are silane compounds having ketoxime groups represented by the following general formula (3):
R
5
a
Si(ON═CR
4
2
)
4-a
(3)
wherein R
4
is independently a substituted or unsubstituted monovalent hydrocarbon group of 1 to 10 carbon atoms, R
5
is an unsubstituted monovalent hydrocarbon group of 1 to 10 carbon atoms, and a is equal to 0, 1 or 2.
Examples of the group represented by R
4
are as listed above for R
1
. R
4
groups may be identical or different. Examples of the group represented by R
5
are unsubstituted ones among those listed above for R
1
.
Illustrative examples of the hydrolyzable silane compound (B) include methyltris(dimethylketoxime)silane, methyltris(methylethylketoxime)silane, ethyltris(methylethylketoxime)silane, methyltris(methylisobutylketoxime)silane, vinyltris(methylethylketoxime)silane, vinyltris(dimethylketoxime)silane, phenyltris(methylethylketoxime)silane, and phenyltris(dimethylketoxime)silane, which fall in the ketoximesilanes of formula (3). Other exemplary silanes are methyltrimethoxysilane, methyltriacetoxysilane, methyltriisopropenoxysilane
Sakamoto Takafumi
Sato Tokuo
Dawson Robert
Shin-Etsu Chemical Co. , Ltd.
Zimmer Marc S.
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