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
2002-05-10
2004-03-23
Robertson, Jeffrey B (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...
C524S301000, C524S430000, C524S432000, C524S433000, C528S012000, C528S014000, C528S019000, C528S033000, C528S034000
Reexamination Certificate
active
06710119
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a condensation curing type room temperature rapid curing organopolysiloxane composition which displays rapid curability and excellent curability of deep sections of the composition.
2. Description of the Prior Art
Conventional condensation curing type room temperature rapid curing organopolysiloxane compositions include single-pack type or one-pack type compositions using an organopolysiloxane terminated with hydroxyl groups at both molecular chain terminals as a base polymer, in which the rate of cross linking due to hydrolysis is increased by reducing the amount of cross linking agent to an absolute minimum, as well as two-pack type compositions in which a base polymer of an organopolysiloxane terminated with hydroxyl groups at both molecular chain terminals, and a cross linking agent are packaged separately.
However, although the aforementioned one-pack type compositions cure rapidly at the composition surface, a certain degree of time is required for deeper sections of the composition to cure, and consequently the compositions cannot really be termed rapid curing compositions. Furthermore, although the aforementioned two-pack type compositions display comparatively good curing of deep sections of the composition, handling is complex as the mixing ratio of the respective contents of the two packs is not 1:1, and the use of such compositions in automated mixing apparatus is also difficult. In addition, in order to ensure complete curing of the deep sections of the composition, either the total amount of hydroxyl groups at both terminals of the organopolysiloxane or polyoxyalkylene polymer and the amount of added cross linking agent need to be very carefully controlled, or additional water needs to be added to act as a curing agent for the deeper sections.
In contrast, an addition curing type organopolysiloxane composition enables a mixing ratio of the respective contents of the two packs of 1:1, and displays superior workability, but typically requires heating in order to achieve curing and adhesion. Furthermore, poisoning of the curing catalyst in the presence of addition poisons limits the operating environment.
Techniques for resolving the problems outlined above include the compositions disclosed in U.S. Pat. No. 5,319,050, in which 0.001 to 1 mol of an organic compound with at least one C═O group within each molecule, and 0.001 to 1 mol of an organic compound with at least one NH
2
group within each molecule, are added to a diorganopolysiloxane with a hydrolysable silyl group at both terminals of the molecular chain. The compositions are room temperature rapid curing organopolysiloxane compositions which utilize water produced as a by-product of a ketimine formation reaction of a C═O group and a NH
2
group. The inventors of the present invention have also confirmed that by using an organopolysiloxane with both terminals blocked with hydroxyl groups as the base polymer, an improvement in curability can be achieved over the case using a diorganopolysiloxane with a hydrolysable silyl group at both terminals of the molecular chain.
However, it has been found that these compositions using the ketimine formation reaction are not so sufficient in rapid curability and curability of deep sections as expected in the case where acetic acid-elimination reaction occurs in crosslinking of compositions.
Furthermore, a moisture curable composition is disclosed in U.S. Pat. No. 5,264,515 in which the curing agent is described as a mixture of zinc oxide and acid. However, no specific description is given of the composition.
SUMMARY OF THE INVENTION
In order to resolve the issues described above, an object of the present invention is to provide a room temperature rapid curing organopolysiloxane composition displays rapid curability at room temperature as well as excellent curability of deep sections of the composition, although it has an acetic acid-elimination type curing mechanism.
As a result of intensive investigation, the inventors of the present invention discovered that in a composition incorporating the constituents (A) to (C) described below, the presence of the constituent (B) and the constituent (C) produces a reaction between the constituent (C) and a carboxylic acid originating from the constituent (B) generated during hydrolysis, which yields water, and this water promotes rapid curing and the curing of deep sections of the composition. In other words, the inventors discovered that this composition not only cures in the presence of moisture in the air, but that this curing also results in the production of water within the composition, enabling the composition to undergo curing not only from the surface, but also from within the composition.
In other words, the present invention provides a room temperature rapid curing organopolysiloxane composition comprising:
(A) 100 parts by weight of a diorganopolysiloxane represented by a general formula (1) shown below,
wherein, each R represents, independently, a substituted or unsubstituted monovalent hydrocarbon group, each X represents, independently, an OH group, an alkoxy group or an acyloxy group, a represents an integer from 0 to 2, and n represents a number which results in a viscosity at 25° C. of 25 to 1,000,000 mm
2
/s;
(B) 2 to 50 parts by weight of either a hydrolysable silane with at least two acyloxy groups within each molecule, a partial hydrolysis-condensation product thereof, or a mixture thereof; and
(C) 5 to 200 parts by weight of an inorganic filler capable of generating water through a reaction with a carboxylic acid generated by hydrolysis of the aforementioned constituent (B).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As follows is a more detailed description of the present invention.
[Constituent (A)]
The constituent (A) is the base polymer of the composition, and forms a cured rubber elastic body on cross linking. The constituent (A) is a diorganopolysiloxane represented by the general formula (1) above, and may be either a single polysiloxane, or a mixture of two or more different polysiloxanes.
In the general formula (1), each R represents, independently, a substituted or unsubstituted monovalent hydrocarbon group. Specific examples of the R group include alkyl groups such as methyl groups, ethyl groups and propyl groups; cycloalkyl groups such as cyclohexyl groups; alkenyl groups such as vinyl groups and allyl groups; aryl groups such as phenyl groups and tolyl groups; and groups in which a portion of the hydrogen atoms of the aforementioned groups have been substituted with halogen atoms such as chloromethyl groups and 3,3,3-trifluoropropyl groups, although methyl groups are preferred.
In the general formula (1), X represents an OH group, an alkoxy group or an acyloxy group, and a represents an integer from 0 to 2, and in those cases in which X is an OH group, polymers in which a=2 are preferred, whereas in those cases in which X is an alkoxy group, polymers in which a=0,1 are preferred. Preferred alkoxy groups include methoxy groups and ethoxy groups, whereas acetoxy groups are the preferred acyloxy group.
Furthermore, the base polymer of the constituent (A) must have a viscosity at 25° C. between 25 and 1,000,000 mm
2
/s, and in the general formula (1), the value of n must produce a viscosity within this range. If the viscosity is outside the above range, then it becomes very difficult to form a cured rubber product with satisfactory characteristics, and the workability of the composition also deteriorates. The viscosity should preferably be from 50 to 50,000 mm
2
/s, and even more preferably from 100 to 20,000 mm
2
/s. In addition, the degree of polymerization of the base polymer is typically at least 10, in order to ensure an organopolysiloxane with a viscosity which falls within the above viscosity range.
[Constituent (B)]
The constituent (B), either a hydrolysable silane with at least two acyloxy groups within each molecule, or a partial hydrolysis-condensati
Kimura Tsuneo
Teshigawara Mamoru
Robertson Jeffrey B
Shin-Etsu Chemical Co. , Ltd.
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