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
2001-08-30
2003-06-24
Lipman, Bernard (Department: 1713)
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...
C106S033000, C106S287260, C523S122000, C524S292000, C524S765000
Reexamination Certificate
active
06583207
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to liquid ester compositions. More particularly, this invention relates to mixtures comprising a diester derived from a dialkylene glycol and benzoic acid or a substituted benzoic acid and a monoester derived from at least one dialkylene glycol or other dihydric alcohol and the same acid. The weight ratio of monoester to diester in the present compositions is sufficient to cause the compositions to be liquids at 28° C. The diester is a solid at this temperature.
The liquid ester compositions of the present invention are particularly suitable plasticizers for aqueous polymer compositions useful as adhesives.
DESCRIPTION OF THE PRIOR ART
Mono- and diesters derived from benzoic acid and dialkylene glycols such as diethylene glycol and dipropylene glycol are known compounds. The use of these diesters alone and in combination with limited amounts of the corresponding monoesters as plasticizers for aqueous polymer emulsions is described in the prior art. As an example of the latter, U.S. Pat. No. 5,676,742, which issued to William Arendt on Oct. 14, 1997 describes plasticized aqueous polymer compositions useful as latex caulks. The primary plasticizer in these compositions is a diester derived from benzoic acid and diethylene and/or dipropylene glycol. Both hydroxyl groups of the diol are esterified.
In accordance with the teaching of the aforementioned patent to Arendt, a shortcoming of caulks formed from aqueous polymer compositions containing dibenzoates of diethylene- and/or dipropylene glycol as plasticizers is the greater susceptibility of the final caulk to fungal attack relative to caulks prepared using the same polymer composition and a diester of phthalic acid such as butylbenzyl phthalate as the plasticizer.
The Arendt patent teaches that even though monoesters of glycols are not considered effective plasticizers for many applications, relatively low levels of diethylene glycol (DEG) monobenzoate and/or dipropylene glycol (DPG) monobenzoate in combination with the corresponding dibenzoate as the primary plasticizer were sufficient to impart fungicidal properties to the caulks without any substantial adverse effect on the processability of the polymer compositions.
Throughout this patent the concentrations of the DEG and DPG monobenzoates in blends containing the corresponding dibenzoates are expressed in terms of a “hydroxyl number”. The units for the “hydroxyl number” are understood by those skilled in the art to be milligrams of potassium hydroxide per gram of sample.
The relationship between the “hydroxyl number” and the relative concentration of monobenzoate in a monobenzoate/dibenzoate blend will be explained in greater detail in a subsequent section of this specification.
The hydroxyl numbers exhibited by the mixtures of diethylene glycol mono- and dibenzoates disclosed in the Arendt patent range from 12.1 to 58.4. This is equivalent to a concentration of diethylene glycol monobenzoate in the mixture of from 4 to 18 weight percent.
It is understood by those skilled in the art that to be effective, a water-insoluble plasticizer should be absorbed by the particles of polymer present in an aqueous emulsion of the polymer. This absorption typically results in an increase in viscosity of the polymer composition. Data in Table 6 of the aforementioned Arendt patent demonstrate significantly less of an increase in viscosity with increasing plasticizer concentration as the hydroxyl number of the plasticizer is increased, which is equivalent to an increased concentration of the corresponding monobenzoate in a monobenzoate/dibenzoate blend. One skilled in the art of polymer chemistry would conclude from these data that the monobenzoates of diethylene and dipropylene glycols are not effective plasticizers for the aqueous polymer compositions described in the patent and would not employ these monobenzoates as plasticizers in aqueous polymer compositions unless fungicidal activity was a requirement for the final product.
The use of the monobenzoate of 2,2,4-trimethyl-1,4-pentanediol as a plasticizer for polyvinyl chloride is described in U.S. Pat. No. 5,006,585, which issued to DiBella on Apr. 9, 1991. Because polyvinyl chloride is processed as a molten material, any adverse effect of the plasticizer on the viscosity or processability of aqueous polymer dispersions is not a consideration. The only criterion for the melting point of the plasticizer is that it be below the melting point of polyvinyl chloride.
The present invention is based on the following unexpected findings.
1. The addition of at least about 30 weight percent of monobenzoates of a specified class of dihydric alcohols and glycols to diethylene glycol dibenzoate, which is a solid at 28° C., results in a mixture that is a liquid at 12° C. Liquid plasticizers are advantageous relative to solid ones because liquids are easier to transport and blend. They also eliminate the need to heat aqueous polymer compositions during or following addition of the plasticizer to ensure uniform distribution of plasticizer throughout the polymer composition and absorption of the plasticizer by the emulsified polymer particles.
2. The reduction in plasticizer efficacy with monobenzoate concentration demonstrated by the data in the aforementioned Arendt patent is not observed when the concentration of monobenzoate is increased beyond the limits taught in this patent. Preferred compositions exhibit an increase in viscosity at least equivalent to that achieved using ethylene gylcol dibenzoate.
U.S. Pat. No. 5,990,214, issued on Nov. 23, 1999 to Arendt et al. discloses mixtures comprising the dibenzoates of DEG and triethylene glycol. These blends exhibit a eutectic freezing point that is below the freezing point of either component diester. No monobenzoates of these glycols are disclosed or suggested in this patent as required or optional plasticizers.
SUMMARY OF THE INVENTION
The present invention provides liquid ester compositions comprising a mixture consisting essentially of:
at least one monoester represented by a formula selected from the group consisting of H[OR
1
]
n
OC(O)R
2
and HOR
3
OC(O)R
2
; and
at least one diester represented by the formula R
2
(O)COCH
2
CH
2
OCH
2
CH
2
OC(O)R
2
;
wherein said diester is a solid at 28° C., each R
1
is alkylene containing 2 or 3 carbon atoms; R
2
is phenyl or substituted phenyl, R
3
is alkylene containing from 2 to 8 carbon atoms, n is 2 or 3, and wherein the concentration of said monoester in said ester compositions is sufficient to render said mixture liquid at 28° C.
The concentration of monobenzoate required to yield a liquid composition is typically at least about 30 weight percent of the mono-/dibenzoate mixture. The present compositions can contain up to 99 weight percent of the present monobenzoates.
This invention also provides plasticized aqueous polymer compositions wherein the polymer is selected from the group consisting of 1) polymerized vinyl esters including but not limited to polyvinyl acetate, and copolymers of said esters with at least one olefin such as ethylene and 2) polymerized esters of ethylenically unsaturated carboxylic acids such as acrylic and methacrylic acids, including copolymers of these esters with olefins such as ethylene and styrene, and 3) condensation polymers such as polyesters and polyamides. The plasticizer comprises a liquid benzoic acid ester composition of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The Dibenzoate Ingredient
The dibenzoate present in the liquid ester compositions of this invention is diethylene glycol (DEG) dibenzoate, represented by the formula R
2
(O)COCH
2
CH
2
OCH
2
CH
2
OC(O)R
2
; wherein R
2
is phenyl or substituted phenyl.
Benzoic acids suitable for use in preparing the present ester compositions can be represented by the general formula HO(O)CAr, wherein Ar represents an unsubstituted or substituted phenyl radical. Substituents that can be present on the phenyl radical include but are not limited to alkyl radicals containing from 1 to about
Arendt William David
Stanhope Bruce Edward
Lipman Bernard
Sidley Austin Brown & Wood LLP
Velsicol Chemical Corporation
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