Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-01-21
2002-02-26
Metzmaier, Daniel S (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S227000, C524S459000, C516S074000, C516S076000, C252S182280, C252S182290, C502S160000
Reexamination Certificate
active
06350835
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an aqueous emulsion of a peroxyester that is liquid at −20° C., which comprises a protective colloid, a non-ionic surfactant, and an anti-freeze agent.
Such peroxide emulsions are known from European Patent No. 32,757. According to this reference, a variety of peroxides, colloids, and surfactants can be used in emulsions that also comprise an anti-freeze agent. For the surfactants and protective colloids of choice, reference is made to U.S. Pat. No. 3,988,261, which lists many such compounds. In respect of one of the listed types of protective colloids, namely, polyvinyl acetate (PVA), it is stated that the degree of hydrolysis will influence the properties. It is suggested to use PVAs with a substantial degree of hydrolysis, e.g. 65% or more. In European Patent No. 32,757, however, only one emulsion is presented which includes a peroxyester, namely, tert-butyl peroxyneodecanoate. In this example, an ethoxylated nonylphenol is used as the surfactant, while xanthan gum is used as the protective colloid.
The protective colloids and surfactants mentioned in U.S. Pat. No. 3,988,261 generally are not suitable for the production of concentrated, storage-stable, and safe peroxyester emulsions such as are widely accepted in polymerization processes. One class of surfactant, namely, the ethoxylated nonylphenol type, is known to be detrimental to the electrical properties of polyvinyl chloride (PVC) when introduced into the polymerization process of vinyl chloride monomer (VCM). Also, it is well-known that the ethoxylated nonylphenols have environmental drawbacks. In regard to the other surfactants that are listed, it is noted that they are generally unacceptable because they typically result in very viscous peroxyester emulsions and/or emulsions that are not safe, particularly when emulsions with a high concentration of perester are produced. It was also found that most of the listed protective colloids, in combination with the suitable surfactants, are not acceptable in the formulation of peroxyesters. The protective colloids mentioned will often result in unacceptable viscosity of the peroxyester emulsion.
Hence, there is a need for concentrated peroxyester emulsions with a low viscosity that are storage-stable, safe, and generally applicable in polymerization processes, particularly those of VCM.
There are various other publications that relate to water-based peroxide dispersions. However, none of them disclose or suggest peroxyester emulsions that satisfy the above-mentioned criteria.
Japanese patent Publication No. 61-130315 (1986) suggests that peroxyester emulsions can be made using a protective colloid, a non-ionic surfactant, and an anti-freeze agent. It is taught that the non-ionic surfactant can be selected from a variety of materials, while the protective colloid must be a product with a high dissolution rate in water, such as modified celluloses and saponified polyvinyl acetates (PVAs). Preferred are PVAs with a degree of hydrolysis greater than 60 mole %. The only exemplified formulations are emulsions of peroxy-dicarbonates. Using these formulations for peroxyesters was found to result in emulsions that do not satisfy the requirements of safety, viscosity, and/or applicability.
British Patent No. 2, 068,008 discloses aqueous peroxide dispersions in which a protective colloid, such as a cellulose or a PVA, is used together with an emulsifier system with an HLB above 15. The emulsifier(s) is/are specified to be non-ionic, ethoxylated, free from cyclic internal ether bonds, and suitably selected from ethoxylated alkylphenols, ethoxylated fatty alcohols, ethoxylated fatty acids, ethoxylated glycol and glycerol fatty esters, and alkylene oxide block copolymers. Although this reference suggests using surfactants with a very high HLB value, it does not suggest to the person of ordinary skill in the art he should make a specific combination of peroxyesters, anti-freeze, PVAS, and surfactants. More specifically, peroxyesters and/or anti-freeze agents are not mentioned at all.
SUMMARY OF THE INVENTION
It has now been found that, surprisingly, improved aqueous peroxyester emulsions can be produced and applied by a proper combination of peroxyester, non-ionic surfactant, and protective colloid. The invention is characterized in that the protective colloid is a polyvinyl acetate with a degree of hydrolysis between 45 and 68% and the non-ionic surfactant has an HLB value of 16 or higher and is selected from alkylene oxide block-copolymers, ethoxylated fatty alcohols, and ethoxylated fatty acids.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In this specification, the term “surfactant” refers to a surface-active chemical that is to be used in the peroxyester formulations according to the invention and that influences the interfacial surface tension between the water and the peroxyester phase. Such compounds are also known as “emulsifiers.” Preferably, the aqueous peroxyester emulsion according to the invention contains only one surfactant with an HLB value of 16 or higher. More preferred are surfactants with an HLB value of 17 or higher, since such surfactants tend to result in less viscous emulsions. If so desired, a mixture of surfactants can be used. In that case, the combined surfactants should have an HLB value of 16 or higher, while it is preferred that all surfactants used have an HLB greater than 10, preferably greater than 12.5, and more preferably of 16 or higher, because surfactants with a lower HLB value can have an adverse effect on the viscosity of the final emulsion. HLB value stands for “hydrophilic-lipophilic balance” as described in “The Atlas HLB-System, a Time Saving Guide to Emulsifier Selection,” published by Atlas Chemical Industries Inc., 1963. For blends of surfactants the HLB value is calculated from the weight ratio of the components, as is also mentioned in this publication.
The non-ionic surfactant or surfactants that can be used in the aqueous emulsions according to the invention are alkylene oxide block-copolymers, ethoxylated fatty alcohols, and ethoxylated fatty acids. The preferred surfactants are ethoxylated fatty alcohols and ethoxylated fatty acids with an HLB value greater than 16. Most preferred are such ethoxylated fatty alcohols. These products were found to be pre-eminently suited to make emulsions with good stability, safety, and viscosity properties at high peroxyester concentrations. The amount of the surfactant or the combination of surfactants in the final emulsion is from 0.05-5 percent by weight (% w/w). Preferably, from 0.1 to 2% w/w of surfactant is used, while an amount between 0.1 and 1% w/w is most preferred.
The protective colloid to be used in the aqueous emulsions according to the invention must be a PVA with a degree of hydrolysis between 45% and 68%. Preferably, the degree of hydrolysis is between 45% and 62.5%. Most preferred is a PVA with a degree of hydrolysis between 50% and 60%. A PVA with a degree of hydrolysis below 45% cannot be used because such a PVA is not soluble in the mixture of water and anti-freeze. A PVA with a degree of hydrolysis greater than 68% resulted in emulsions with a too high viscosity. Instead of using just one type of PVA, also a blend of two or more PVAs can be used. In that case the blend can be seen as just one PVA of which the degree of hydrolysis is the weight average degree of hydrolysis of the PVAs. Preferably, such a blend of PVAs does not comprise a PVA with a degree of hydrolysis below 45% or above 68%, for the above-mentioned reasons.
The amount of PVA used in the emulsions according to the invention will depend on the concentration and the types of peroxyester and surfactant used and the desired viscosity of the final emulsion. Typically, the amount of PVA in the final emulsion will be between 0.5 and 10% w/w. The use of these protective colloids in combination with the above-mentioned surfactants allows the production of concentrated, storage-stable, and safe peroxyester emulsions.
The anti-freeze used in the emulsions accordin
O Boen Ho
Westmijze Hans
Akzo Nobel NV
Fennelly Richard P.
Metzmaier Daniel S
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