Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1995-02-17
1997-01-14
Zitomer, Fred
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525 60, 525 62, 525383, C08F 828
Patent
active
055940692
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a process for producing mixed poly(vinyl acetal)s and more particularly to a process for producing partial polyvinyl butyral containing unreacted vinyl alcohol groups which is modified with long chain acetal groups.
Polyvinyl butyral is used as sheet in transparent laminated glazings, adhesive compositions, protective coatings, photoimaging applications, binders for ceramics and the like. Such resin contains 10 to 30 weight % unreacted vinyl alcohol groups and is hereinafter called "partial polyvinyl butyral" or "partial PVB". Partial polyvinyl butyral can be modified by including long chain acetal groups in the polymer for internal plasticizing, such partial polyvinyl butyral containing long chain acetal groups hereinafter called "mixed poly(vinyl acetal)s". In this regard note U.S. Pat. No. 5,137,954, issued Aug. 11, 1992. Such long chain acetal groups can broaden the utility of a mixed poly(vinyl acetal). For example, U.S. Pat. No. 5,137,954 discloses use of mixed poly(vinyl acetal)s with reduced amounts of external plasticizer and U.S. Pat. No. 5,019,624 discloses mixed poly(vinyl acetal)s without external plasticizer.
The size of resin particles formed during synthesis of partial PVB and mixed poly(vinyl acetal)s is important, particularly for laminated glazing applications. Particles too large can vary in hydroxyl content within the particle and can appear as visual defects in the transparent sheet of the glazing; particles too small present handling problems during formulation with other materials and can be an explosion hazard.
Partial PVB and mixed poly(vinyl acetal)s have been synthesized by acetalizing polyvinyl alcohol with butyraldehyde or mixtures of butyraldehyde and another aldehyde at low temperature on the order of 5.degree.-20.degree. C., followed over time as the reaction continues by a slow increase to about 50.degree.-90.degree. C. In this regard, note Example 1 of U.S. Pat. No. 5,137,954. When two aldehydes were used in such prior art, simultaneous formation of both acetal linkages occurred during the acetalization reaction. As far as is known, this acetalization temperature profile in the prior art was apparently intended to provide the desired resin particle size and minimize problems just referred to.
SUMMARY OF THE INVENTION
Now improvements have been made to optimize the process for producing mixed poly(vinyl acetal)s.
Accordingly, a principal object of this invention is to improve the process for producing mixed poly(vinyl acetal)s.
Another object is to provide an industrially valuable, high temperature, reduced cycle time process for preparing mixed poly(vinyl acetal)s.
A further object is to provide a process technique reducing the size and improving the size distribution of particles of mixed poly(vinyl acetal)s during their synthesis.
Another object is to make mixed poly(vinyl acetal)s without using low-temperature in the synthesis process.
Other objects will in part be obvious and will in part appear from the following description and claims.
These and other objects are accomplished by a process for producing mixed poly(vinyl acetal)s containing butyral acetal groups and long chain acetal groups derived from-one or more aldehydes containing at least six C atoms which comprises a) conducting an acetalization reaction forming long chain acetal groups in the substantial absence of butyraldehyde until gel break (hereinafter defined) occurs, b) adding butyraldehyde after gel break, and c) continuing acetalization until the desired reaction end point is reached.
In another aspect, there is provided, in a process for producing partial polyvinyl butyral modified with long chain acetal groups which comprises a) acetalizing polyvinyl alcohol with butyraldehyde in the presence of an acid catalyst to form partial polyvinyl butyral having about 10 to 30 weight percent unreacted vinyl alcohol groups and b) neutralizing the partial polyvinyl butyral with a base, the step in combination therewith of: c) condensing the polyvinyl alc
REFERENCES:
patent: 2116635 (1938-05-01), Matheson
patent: 5019624 (1992-05-01), Gutweiler et al.
patent: 5137954 (1992-08-01), DasGupta
David Donald J.
Rotstein Nestor A.
Monsanto Company
Zitomer Fred
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