Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
1996-05-15
2002-04-09
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C525S403000
Reexamination Certificate
active
06369187
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a novel oxypropylene polymer which contains a reactive silicon group and to a method of producing the same.
So far, various room temperature curing polymers have been developed which can be cured to rubber-like substances by the action of moisture. Thus, oxypropylene polymers containing a reactive silicon group (a group which is a silicon atom-containing group with a hydroxyl group or a hydrolyzable group being bound to the silicon atom and can form a siloxane bond) are also known.
However, since it is difficult to produce high molecular weight polyoxypropylene with a narrow molecular weight distribution (great monodispersity), the known reactive silicon group-containing polyoxypropylene species are only those showing a broad molecular weight distribution (great polydispersity).
Recently, it has been reported that polyoxypropylene with a narrow molecular weight distribution can be obtained. The present inventors found that polymers derived from polyoxypropylene having a narrow molecular weight distribution, which is used as the main chain, by introducing a reactive silicon group and a urethane bond terminally to the main chain, have a low viscosity, hence are easy to handle, before curing and, after curing, give cured products having excellent tensile characteristics as well as good chemical resistance and water resistance. This finding has now led to the present invention.
SUMMARY OF THE INVENTION
The reactive silicon group-containing oxypropylene polymer of this invention is an oxypropylene polymer the main polymer chain of which is essentially composed of a repeating unit of the formula
and which has at least one terminal reactive silicon group and at least one terminal urethane bond. It has an {overscore (M)}w/{overscore (M)}n ratio of not more than 1.5 and a number average molecular weight of not less than 3,000.
The production method of this invention is characterized by reacting an oxypropylene polymer having an {overscore (M)}w/{overscore (M)}n ratio of not more than 1.5 and a number average molecular weight per terminal functional group of not less than 1,500 with a compound having a reactive silicon group and an isocyanato group.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The “reactive silicon group” as so termed herein is not limited to any particular species but may typically include groups of the general formula (1) shown below:
In the above formula, R
1
and R
2
each is an alkyl group containing 1 to 20 carbon atoms, an aryl group containing 6 to 20 carbon atoms, an aralkyl group containing 7 to 20 carbon atoms or a triorganosiloxy group of the formula (R′)
3
SiO—. Where there are two or more R
1
or R
2
groups, they may be the same or different. R′ is a monovalent hydrocarbon group containing 1 to 20 carbon atoms. The three R′ groups may be the same or different. X is a hydroxyl group or a hydrolyzable group and, where there are two or more X groups, they may be the same or different. a is 0, 1, 2 or 3 and b is 0, 1 or 2. The number b may vary in the m groups of the formula
m is an integer of 0 or 1 to 19. The following condition shall be satisfied: a+&Sgr;b≧1.
The hydrolyzable group represented by the above-mentioned X is not particularly limited but may be any hydrolyzable group known in the art. More specifically, there may be mentioned a hydrogen atom, a halogen atom, an alkoxy group, an acyloxy group, a ketoximato group, an amino group, an amido group, an acid amido group, an aminoxy group, a mercapto group, an alkenyloxy group and the like. Among these, the hydrogen atom and alkoxy, acyloxy, ketoximato, amino, amido, aminoxy, mercapto and alkenyloxy groups are preferred. From the viewpoint of mild hydrolyzability and easy handling, alkoxy groups are particularly preferred.
One to three such hydrolyzable groups or hydroxyl groups may be bound to one silicon atom, and (a+&Sgr;b) is preferably equal to 1 to 5. Where there are two or more hydrolyzable groups or hydroxyl groups in the reactive silicon group, they may be the same or different.
The reactive silicon group may contain one silicon atom or two or more silicon atoms. In the case of a reactive silicon group comprising silicon atoms linked to one another via a siloxane bonding or the like, the group may contain about 20 silicon atoms.
Reactive silicon groups of the following general formula (2) are preferred because of ready availability.
In the above formula, R
2
, X and a are as defined above.
Specific examples of R
1
and R
2
appearing in the general formula (1) given hereinabove include, among others, alkyl groups, such as methyl and ethyl, cycloalkyl groups, such as cyclohexyl, aryl groups, such as phenyl, aralkyl groups, such as benzyl, and triorganosiloxy groups of the formula (R′)
3
SiO— in which R′ is methyl or phenyl. Among these, methyl is particularly preferred.
The oxypropylene polymer should recommendably contain at least one, preferably 1.1 to 5 reactive silicon groups per molecule thereof. When the number of reactive silicon groups contained in the polymer on a per-molecule basis is less than 1, the curability becomes inadequate and good rubber elastic behavior can hardly be developed.
The oxypropylene polymer contains at least one reactive silicon group terminally to the molecular chain thereof. It may contain a reactive silicon group internally to the chain. When the reactive silicon group occurs terminally to the molecular chain, as in the present invention, the oxypropylene polymer component contained in the finally-formed cured products can have an increased number of effective network chains and therefore a rubber-like cured product showing high strength and high elongation (low elasticity) can readily be obtained.
The “urethane bond” so termed herein means a bond represented by —NHCOO—.
The oxypropylene polymer, which constitutes the main polymer chain in the polymer of this invention, is essentially composed of a repeating unit of the formula
This oxypropylene polymer may be straight-chained or branched, or a mixture of these. It may further contain a small proportion of another monomer unit or the like.
The oxypropylene polymer that can effectively be used has a number average molecular weight of not less than 3,000. The number average molecular weight of the polymer should preferably be not less than 3,000 when the polymer is straight-chained, and not less than 5,000 when the polymer is branched. More preferably, the polymer should have a number average molecular weight of 6,000 to 30,000. Furthermore, in this oxypropylene polymer, the weight average molecular weight
umber average molecular weight ratio ({overscore (M)}w/{overscore (M)}n) is not more than 1.5, hence the molecular weight distribution is very narrow (the monodispersity is great). The value of {overscore (M)}w/{overscore (M)}n should preferably be not more than 1.4, more preferably not more than 1.3. The molecular weight distribution can be measured by various methods. Generally, however, the measurement method most commonly used is gel permeation chromatography (GPC). Since the molecular weight distribution is narrow in that manner despite the great number average molecular weight, the polymer of the invention has a low viscosity before curing, hence is easy to handle and, after curing, shows good rubber elastic behavior.
The polymer of this invention has a terminal urethane bond, so that the cured products after curing are excellent in strength and elongation.
For producing the reactive silicon group-containing oxypropylene polymer of the invention, it is only necessary to react an oxypropylene polymer having a terminal functional group (hereinafter referred to as functional group Y), such as a hydroxyl group, with a compound having a reactive silicon group and an isocyanato group reactive with functional group Y.
The functional group Y-containing oxypropylene polymer to be used should be an oxypropylene polymer having an {overscore (M)}w/{overscore (M)}n ratio of not more than 1.5 and a number average molecu
Fujita Masayuki
Homma Michihide
Wakabayashi Hiroshi
Jordan and Hamburg LLP
Kanegafuchi Chemical Industry Co. Ltd.
Short Patricia A.
LandOfFree
Reactive silicon group-containing oxypropylene polymer and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reactive silicon group-containing oxypropylene polymer and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reactive silicon group-containing oxypropylene polymer and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2860529