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
2002-04-25
2004-08-10
Robertson, Jeffrey B. (Department: 1712)
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...
C524S267000, C525S100000, C525S101000, C525S105000, C525S106000
Reexamination Certificate
active
06774167
ABSTRACT:
The invention relates to a process for reducing undesirable changes in shade brought about by low temperatures (Cold Stress Whitening) in impact-modified thermoplastic molding compositions F which comprise at least one elastomeric graft polymer A and at least one thermoplastic polymer B, in which from 10 to 200 ppm, based on the molding compositions F, of at least one polyorganosiloxane S are added to the impact-modified thermoplastic molding composition F. The invention further relates to the use of polyorganosiloxanes for reducing cold stress whitening in the impact-modified thermoplastic molding compositions F.
Impact-modified thermoplastic molding compositions based on elastomeric graft polymers and on thermoplastic matrix polymers, e.g. ABS (acrylonitrile-butadiene-styrene), ASA (acrylonitrile-styrene-alkyl acrylate) and AES (acrylonitrile-EPDM-styrene, EPDM=ethylene-propylene-diene monomer), have a wide variety of application sectors since they have an advantageous property profile. The molding compositions are usually used as pellets which are then further processed to give moldings, for example by injection molding or extrusion.
When the pellets or the moldings are stored or transported at low temperatures, in particular temperatures below −10° C., an undesirable change in shade can occur, mostly visible as a whitening effect. This effect is known as cold stess whitening (hereinafter CSW) and is naturally particularly disturbing in the case of pigmented pellets or moldings, since the original shade established using colorants is lost. At temperatures below −20° C., as frequently found during transport and storage in winter and in northern countries, cold stress whitening is particularly pronounced.
CSW is usually determined by color coordinate measurements in the form of a color deviation dE. A dE>3 means severe CSW and generally exceeds the acceptable range.
EP-A 44 143 discloses molding compositions made from impact-modified polystyrene to which certain organopolysiloxanes are added to reduce the coefficient of friction. The CSW is not mentioned.
DE-A 28 27 594 describes ABS molding compositions which comprise from 0.05 to 0.5% by weight of a liquid polymethylphenylsiloxane or polydimethylsiloxane, and comprise other additives. This is intended to improve the notched impact strength and other mechanical properties (ball indentation hardness, Vicat softening point, flowability) of the ABS. The phenomenon of CSW is not mentioned.
Research Disclosure 223 020 discloses the use of a siloxane polymer for improving the elongation at break of rubber-modified molding compositions. From 0.01 to 1% by weight of the siloxane polymer is used here. CSW is not mentioned.
EP-A 177 096 describes ABS molding compositions to which from 0.1 to 3% by weight silicone oil is added to improve impact strength and flow properties. CSW is not mentioned.
DE-A 20 39 022 describes molding compositions made from butadiene rubber, styrene, methyl methacrylate and acrylonitrile which comprise from 0.01 to 3% by weight of polyorganosiloxane, and this is intended to improve the notched impact strength and transparency. Here, again, CSW is not mentioned.
It is an object of the present invention to provide a process which can produce impact-modified thermoplastic molding compositions with markedly reduced CSW (dE≦3). The reduction in CSW should not be associated with any impairment of other advantageous properties of the molding compositions. In particular, the process should not give any impairment of mechanical properties, such as impact strength, modulus of elasticity, elongation at break and flowability, nor of processing properties (e.g. mold-release performance, mold-deposit formation, exudation) of the molding.
We have found that this object is achieved by the process defined at the outset. The use of polysiloxanes for reducing CSW in impact-modified thermoplastic molding compositions F has also been found.
The novel process is described in greater detail below.
The impact-modified thermoplastic molding compositions F contain at least one elastomeric graft polymer A. Preference is given to the use of graft polymer A which contain, as rubber,
diene rubber based on dienes such as butadiene or isoprene,
an alkyl acrylate rubber based on alkyl acrylates such as n-butyl acrylate or 2-ethylhexyl acrylate, or,
an EPDM rubber based on ethylene, propylene and a diene,
or mixtures of these rubbers and, respectively, rubber monomers.
Preferred graft polymers A comprise, based on A),
a1) from 30 to 95% by weight, preferably from 40 to 90% by weight and particularly preferably from 40 to 85% by weight, of an elastomeric base made from, based on a1)
a11) from 50 to 100% by weight, preferably from 60 to 100% by weight and particularly preferably from 70 to 100% by weight, of a C
1
-C
10
-alkyl acrylate,
a12) from 0 to 10% by weight, preferably from 0 to 5% by weight and particularly preferably from 0 to 2% by weight, of a polyfunctional crosslinking monomer, and
a13) from 0 to 40% by weight, preferably from 0 to 30% by weight and particularly preferably from 0 to 20% by weight, of one or more monoethylenically unsaturated monomers,
or from
a11*) from 50 to 100% by weight, preferably from 60 to 100% by weight and particularly preferably from 65 to 100% by weight, of a diene with conjugated double bonds, and
a12*) from 0 to 50% by weight, preferably from 0 to 40% by weight and particularly preferably from 0 to 35% by weight of one or more monoethylenically unsaturated monomers,
or from
a11**) from 50 to 100% by weight, preferably from 60 to 100% by weight and particularly preferably from 65 to 100% by weight of a mixture made from ethylene, propylene and a diene, and
a12**) from 0 to 50% by weight, preferably from 0 to 40% by weight and particularly preferably from 0 to 35% by weight, of one or more other monoethylenically unsaturated monomers,
a2) from 5 to 70% by weight, preferably from 10 to 60% by weight and particularly preferably from 15 to 60% by weight, of a graft made from, based on a2),
a21) from 50 to 100% by weight, preferably from 60 to 100% by weight and particularly preferably from 65 to 100% by weight, of a styrene compound of the formula
where R
1
and R
2
are hydrogen or C
1
-C
8
-alkyl,
a22) fom 0 to 40% by weight, preferably from 0 to 38% by weight and particularly preferably from 0 to 35% by weight, of acrylonitrile or methacrylonitrile or mixtures of these, and
a23) from 0 to 40% by weight, preferably from 0 to 30% by weight and particularly preferably from 0 to 20% by weight, of one or more other monoethylenically unsaturated monomers.
Particularly suitable C
1
-C
10
-alkyl acrylates, component a11), are ethyl acrylate, 2-ethylhexyl acrylate and n-butyl acrylate. Preference is given to 2-ethylhexyl acrylate and n-butyl acrylate, and very particular preference to n-butyl acrylate. It is also possible to use mixtures of various alkyl acrylates which have different alkyl radicals.
Crosslinking monomers a12) are bi- or polyfunctional comonomers having at least two olefinic double bonds, such as butadiene or isoprene, divinyl esters of dicarboxylic acids, such as succinic acid or adipic acid, diallyl or divinyl ethers of dihydric alcohols, such as those of ethylene glycol and of 1,4-butanediol, diesters of acrylic acid or methacrylic acid with the dihydric alcohols mentioned, 1,4-divinylbenzene and triallyl cyanurate. Particular preference is given to tricyclodecenyl acrylate (see DE-A 12 60 135), known by the name dihydrodicyclopentadienyl acrylate, and also to allyl acrylate and allyl methacrylate.
Crosslinking monomers a12) may be present or absent in the molding compositions, depending on the nature of the molding compositions to be prepared, in particular depending on the desired properties of the molding compositions.
If crosslinking monomers a12) are present in the molding compositions, the amounts are from 0.01 to 10% by weight, preferably from 0.3 to 8% by weight and particularly preferably from 1 to 5% by weight, based on a1).
Examples of the other mon
Breulmann Michael
Duijzings Wil
Güntherberg Norbert
Niessner Norbert
Oepen Sabine
BASF - Aktiengesellschaft
Keil & Weinkauf
Robertson Jeffrey B.
LandOfFree
Method for reducing cold stress whitening does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for reducing cold stress whitening, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for reducing cold stress whitening will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3311926