Room temperature curable compositions

Details Room temperature curable compositions Room temperature curable compositions

2002-02-08

2004-06-22

Moore, Margaret G. (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From silicon reactant having at least one...

C528S021000, C528S035000, C524S490000

Reexamination Certificate

active

06753398

ABSTRACT:

This invention relates to room temperature curable compositions, and more particularly, to room temperature curable compositions of the condensation curing type having fast curing and deep curing capabilities.
BACKGROUND OF THE INVENTION
Nowadays elastic sealing materials are widely employed in a variety of applications, typically in buildings and automobiles. On use, sealing materials are filled in joints and gaps between various members for forming water- and gas-tight seals. The sealing materials are therefore required, after being filled in joints or around window frames, to quickly cure and form a firm bond to various substrates, typically of inorganic materials such as glass, ceramics, metals, cement and mortar and organic materials such as plastics.
Room temperature fast curable saturated hydrocarbon polymer compositions are known effective as the sealing material. For improving the adhesion of such compositions, a primer composition and a bonding method have been proposed as disclosed in JP-A 11-209701. However, these compositions are not satisfactory in curing capability and a need exists for further improvements in curing performance.
SUMMARY OF THE INVENTION
An object of the invention is to provide a room temperature fast curable composition of the condensation curing type which is improved in curability, especially in fast curing at room temperature and curing to depth.
It has been found that blending (A) a saturated hydrocarbon polymer having a number average molecular weight in the range of 500 to 50,000 and bearing at least two hydrolyzable silyl groups at an end of the backbone and/or an end of a side chain per molecule, with (B) an organic compound having at least one C═O group in a molecule, and (C) an organic compound having at least one NH
2
group in a molecule, the C═O group in component (B) and the NH
2
group in component (C) being selected so as to be reactive with each other, leads to a room temperature fast curable composition of the condensation curing type which is improved in both fast curing at room temperature and curing to depth.
Room temperature fast curable organopolysiloxane compositions of the condensation curing type known in the art include compositions of one part type comprising a both end hydroxy-terminated organopolysiloxane as a base polymer and a crosslinking agent in an amount minimized so as to increase the rate of crosslinking through hydrolysis, and compositions of two part type wherein a both end hydroxy-terminated organopolysiloxane as a base polymer and a crosslinking agent are separately packed.
The compositions of one part type, however, are not regarded as fast curing since they merely have a high curing rate from the surface and require a certain time for deep curing. By contrast, the compositions of two part type are relatively fast in depth curing, but are difficult to handle on account of a mixing ratio of the two parts departing from 1:1 and thus inapplicable to an automatic mixing dispenser. In order to drive complete curing to depths, the quantity of hydroxyl at both ends of organopolysiloxane or polyoxyalkylene polymer and the quantity of crosslinking agent added must be strictly controlled, or water must be further added as a deep curing agent.
On the other hand, organopolysiloxane compositions of the addition curing type are efficient to work since the two parts are mixed in a ratio of 1:1. However, the working environment is limited since a heating oven is generally necessary for curing and the curing catalyst can be poisoned in the presence of an addition poison.
To solve these problems, we proposed in JP-A 5-279570 a composition comprising a diorganopolysiloxane or polyoxyalkylene as a base polymer, an organic compound having a double bond in the form of a C═O group and an organic compound having a NH
2
group wherein instead of directly adding water necessary for condensation curing, water is generated within the composition by reaction between the organic compounds. The composition is improved in deep curing and fast curing properties. However, the silicone base compositions are less stain resistant as the sealing agent, and the polyether base compositions are insufficient in durability and curability. Where saturated hydrocarbon polymers are used, stain resistance is good, but curability is very low as compared with silicone base compositions.
Continuing investigations, we have found that in the composition comprising the saturated hydrocarbon polymer (A), organic compound (B) and organic compound (C), crosslinking reaction takes place between a hydrolyzable silyl group at an end of the backbone and/or a side chain of the saturated hydrocarbon polymer (A) and air-borne moisture, and in parallel therewith, dehydration condensation reaction takes place between compound (B) and compound (C) according to the following scheme (I):
R
2
C═O+H
2
NR′→R
2
C═NR′+H
2
O  (I)
wherein R and R′ are organic groups, allowing crosslinking reaction to proceed with the water generated in depth within the composition as well. As a result, the inventive composition is improved in fast curing and also drastically improved in deep curing. Additionally, the composition has good stain resistance and durability.
This also overcomes the problems of water separation and a decline of workability due to increased thixotropy as found in prior art compositions wherein water is added as a deep curing agent. The present invention is predicated on these findings.
Accordingly, the invention provides a room temperature curable composition comprising (A) 100 parts by weight of a saturated hydrocarbon polymer having a number average molecular weight in the range of 500 to 50,000 and bearing at least two hydrolyzable silyl groups at an end of the backbone and/or an end of a side chain per molecule, (B) an organic compound having at least one C═O group in a molecule, in such an amount as to give 0.001 to 1 mol of the C═O group per 100 parts by weight of polymer (A), and (C) an organic compound having at least one NH
2
group in a molecule, in such an amount as to give 0.001 to 1 mol of the NH
2
group per 100 parts by weight of polymer (A), components (B) and (C) being selected such that the C═O and NH
2
groups in the respective components are reactive with each other.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Component (A)
Component (A) is a base polymer. Any of saturated hydrocarbon polymers excluding polyether polymers is used. The saturated hydrocarbon polymer must have at least two hydrolyzable silyl groups at an end of the backbone and/or an end of a side chain per molecule. Owing to the presence of hydrolyzable silyl groups, the base polymer undergoes hydrolysis and polycondensation in the presence of air-borne moisture and water generated by reaction of components (B) and (C) to be described later, forming a cured product of rubber elastomer.
The hydrolyzable silyl group is defined as a silicon atom having at least one hydrolyzable group attached thereto and represented by the following formula.
Herein X is a hydrolyzable group, p is an integer of 1 to 3, and R
1
is a substituted or unsubstituted monovalent hydrocarbon group. Examples of the hydrolyzable group (X) include carboxyl, ketoxime, alkoxy, alkenoxy, amino, aminoxy, and amide groups. The hydrolyzable group attached to a single silicon atom is not limited to one, and two or three hydrolyzable groups may be attached to a common silicon atom. Another organic group or groups may, of course, be attached to the silicon atom having the hydrolyzable group or groups attached thereto. Examples of the organic groups (R
1
) include alkyl groups such as methyl, ethyl and propyl, cycloalkyl groups such as cyclohexyl, alkenyl groups such as vinyl and allyl, aryl groups such as phenyl and tolyl, and substituted ones of the foregoing groups in which some hydrogen atoms are replaced by halogen atoms or the like, such as chloromethyl and 3,3,3-trifluoropropyl.
The base polymer (A) should have a number average molecul

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