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
2000-01-07
2002-03-12
Michl, Paul R. (Department: 1714)
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...
C560S172000, C560S174000, C560S178000
Reexamination Certificate
active
06355713
ABSTRACT:
The present invention pertains to the use of &bgr;-ketoesters and their enamines for stabilising thermoplastic polymers.
The use of &bgr;-ketoesters for stabilising polymers, especially vinyl chloride polymers, is known in the art. EP-A-433230 discloses alkylene and alkylenoxy &bgr;-ketoesters such as butanediol bis-benzoylacetate and trimethylolpropane tris-acetoacetate, as stabilisers for chlorine-containing polymers. Similarly, JP-A-6-65458 (Chem. Abstr. 121 (1994) 135609t) describes a combination of ethyleneglycol diacetoacetate, a metal alkanoate and a phenolic antioxidant to be used for thermal stabilisation and colour protection in PVC.
Alkanolamide &bgr;-ketoalkanoates such as tris-acetoacetoxyethyl isocyanurate as stabilisers for chlorine-containing polymers are described in EP-A-22749. &bgr;-Ketones constitute another group of useful stabilisers. An effective but expensive &bgr;-ketone stabiliser is stearoyl benzoyl methane, commercially available as Rhodiastab 50®.
Mixtures of stabilisers containing at least a disaccharide alcohol such as maltitol or isomaltitol and a zinc compound (zinc stearate) are disclosed in EP-A-677549. These mixtures result in improved heat stability of polyvinyl-chloride compositions.
EP-A-599478 discloses the use of acetoacetate esters and their enamines, including sorbitol acetoacetate and trimethylolpropane acetoacetate, as a coalescent in water-based acrylic polymers.
EP-A-114270 describes isosorbide mono-acetoacetate and isosorbide mono-&bgr;-amino-crotonate as intermediates in the preparation of isosorbide dihydronicotinate derivatives as anti-hypertensive drugs.
It was found that specific &bgr;-ketoesters and their enamines, which can be obtained from inexpensive natural raw materials, have improved stabilising capacities for use in thermoplastic polymers such as PVC. These &bgr;-ketoesters not only improve the initial colour stability of polymers, but also increase the thermal stability of the polymers. They can be used in rigid polymers, and they are also effective in stabilising flexible polymers. They have an improved performance to cost ratio. The &bgr;-ketoesters and their enamines to be used according to the invention are derived from alcohols or polyols which are natural products or can be obtained from natural products by reduction or chemical and fermentative processes. They are defined in the appending claims. It may be noted that although the &bgr;-keto-esters and the corresponding amines are represented in the formulae 1 and 2 as diketo compounds and keto-enamines respectively, they can also exist in their tautomeric forms of keto-enols and ketoimines, respectively, as in formulae 1a and 2a given below. All these and other tautomeric forms are understood to be included in the formulae used.
A[(O—CHR
4
—Z—CHR
5
)
m
—O—CO—CR
1
═C(OH)—R
3
]
n
1a
A[(O—CHR
4
—Z—CHR
5
)
m
—O—CO—CHR
1
—C(═NR
2
)—R
3
]
n
2a
The group A in the ketoester and enamine thereof according to the invention may be substituted by an aryl group, in particular phenyl, benzyl or phenethyl, which is optionally substituted by hydroxy and/or C
1
-C
4
alkyl. As an example, one or more free hydroxy groups of the polyol, i.e. hydroxyl groups not esterified with &bgr;-keto acid, may be esterified with benzoic acid or with 3-(3,5-di-t-butyl-4-hydroxyphenyl)propanoic acid (antioxidant group), or two of such free hydroxyl groups may be acetalised with a substituted benzaldehyde.
Examples of the &bgr;-ketoesters and enamines to be used according to the invention are ketoesters of lactic acid esters, i.e. &agr;-(&bgr;-ketoacyloxy)propionic acid esters, such as ethyl, butyl, lauryl, stearyl, and especially phenyl, 3,5-di-t-butyl-4-hydroxybenzyl and 2,2,6,6-tetramethyl-4-piperidyl esters.
A very useful group of &bgr;-ketoesters and enamines is derived from sugars, sugar alcohols, dehydrated sugar alcohols and oligosaccharides. These are polyols, which preferably contain more than one &bgr;-ketoester or enamine groups. Suitable sugars comprise glucose, galactose, fructose, (iso)maltulose, leucrose, lactose, sucrose, glucose oligomers such as trehalose, maltose, isomaltose, cellobiose, and higher homologues, such as maltotriose and cyclodextrins, fructose oligomers (especially inulin derivatives) and mixed oligomers and mixtures of these sugars, as well as glycosides of reducing sugars. Oligosaccharides are understood as short-chain polysaccharides having an average degree of polymerisation up to 40 monosaccharide units. Suitable sugar alcohols include xylitol, arabinitol, sorbitol, mannitol, galactitol, lactitol, maltitol, isomaltitol, maltotriitol and the like, and dehydration products thereof such as sorbitan, galactitan, isosorbide and other dianhydroglycitols such as isomannide and isoidide. As explained above, part of the polyol hydroxy groups may be free or be esterified or etherified with other groups, such as aryl groups.
&bgr;-Ketoesters and their enamines of sugar acids and their esters, i.e. where the &bgr;-ketoacyl groups or &bgr;-aminocrotonoyl groups are attached to the hydroxy groups of the sugar acids or their esters, are also effective stabilisers according to the invention. Suitable sugar acids include the glyconic, glycuronic and glycaric acids such as gluconic acid, lactobionic acid and the like, and acids which can be obtained by oxidation or fermentation processes from sugars, such as lactic acid, citric acid, malic acid, tartaric acid, gluconic acid, L-ascorbic acid and the like.
The ketoester groups may be aliphatic groups, such as acetoacetyl, pivaloylacetyl, stearoylacetyl or methoxycarbonyl-acetoacetyl (the monoester of 3-oxoglutaric acid), but they may also contain aryl groups, such as in benzoylacetyl and ring-substituted derivatives thereof. The enamines of the ketoesters such as &bgr;-aminocrotonates and N-substituted &bgr;-aminocrotonates, are equally suitable.
The &bgr;-ketoesters can be prepared in a manner known per se, e.g. by reacting the alcohol or polyol, i.e. the hydroxyalkanoic ester, sugar, sugar acid or sugar alcohol, with a lower alkyl ester of the &bgr;-ketoacid with or without a transesterification catalyst such as a tetra-alkoxytin. It was found that such a catalyst is not necessary for the compounds of the invention, and that the purity of the products is even higher when a catalyst is not used. The absence of a catalyst has as a further advantage that traces of water do not affect the transesterification efficiency. Instead of using a lower alkyl ester of the &bgr;-keto acid, the synthesis can also be performed using a diketene (4-alkylidene-2-oxo-oxetane) with the appropriate alcohol or polyol or dianhydroglycitol. Prior to the reaction of the alcohol or polyol with the &bgr;-ketoacid lower alkyl ester or diketene, it may reacted with an epoxide such as ethylene oxide, propylene oxide or glycidol, eventually resulting in a &bgr;-ketoacid ester having one or more alkylenoxy groups interposed between the &bgr;-ketoacyl group(s) and the alcohol or polyol residue. The &bgr;-aminocrotonates can be prepared by simply reacting the &bgr;-ketoester with ammonia or with an amine such as methylamine or ethanolamine.
The &bgr;-ketoesters and their enamines can be used in polymer compounds in a manner known per se. The stabilisers can be mixed with other additives, such as impact modifiers for rigid formulations (for example chlorinated polyethylene or butadiene/styrene/(acrylonitrile) co- or ter-polymers), plasticisers for flexible formulations (for example phthalic esters such as dibutyl phthalate or dioctyl phthalate, aliphatic monobasic or dibasic esters such as butyl oleate, epoxidised soybean oil, dioctyl adipate), fillers, pigments, flow modifiers (for example acrylates), lubricants (for example calcium stearate, zinc stearate, fatty esters and amides), flame retardants (for example aluminium hydroxide, antimony trioxide), phosphites (for example triaryl phosphites or aryl-alkyl phosphites), antioxidants (for example hindered phenols), HALS (hindered amine light stabiliser)
Frissen Augustinus Emmanuel
Kroon Erica Gertruda Arnolda
Luitjes Hendrikus
Peters Frans Jeanette Maria Leonardus
Schmets Gerard Hubert
Akcros Chemicals
Michl Paul R.
Young & Thompson
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