Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-03-13
2004-05-18
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S123000, C524S130000, C524S154000, C524S238000
Reexamination Certificate
active
06737457
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to thermoplastic molding compositions and more particularly to compositions having good mold release properties.
SUMMARY OF THE INVENTION
The use of zwitterionic compounds as mold release agents in thermoplastics is disclosed. Molding compositions having good release properties, preferably compositions containing polycarbonate resins are thus disclosed.
BACKGROUND OF THE INVENTION
Patents and publications which disclose the de-molding effect of various additives in thermoplastics in general and polycarbonate in particular are known. The substances used most frequently as mold release agents are the esters of long-chain aliphatic acids and alcohols. The use of esters of fatty acid alcohols or polyols, such as e.g. pentaerythrite, with fatty acids is mentioned by way of example, as disclosed in DE-A 33 12 158, EP-A 100 918, EP-A 103 107, EP-A 561 629, EP-A 352 458, EP-A 436 117, or of esters of Guerbet alcohols in U.S. Pat. No. 5,001,180, DE-A 33 12 157, U.S. Pat. No. 5,744,626 or of montanic acids as acid components in U.S. Pat. No. 4,097,435. A disadvantage is that the fatty acid esters do not have a clear de-molding effect until they are present in quantities of more than 0.5 wt. %. However, these concentrations often produce haze and/or the formation of mold deposits. Siloxanes, also known as mold release agents (cf. U.S. Pat. Nos. 4,536,590, 4,390,651, 3,751,519), are not very compatible with polycarbonate and produce haze in the concentrations required for effectiveness. &agr;-Olefin polymers (EP-A 561 630, EP-A 230 015) with residual double bonds (DE-A 32 44 499) are not color-fast. With hydrogenated systems, as with the long-chain alkanes (U.S. Pat. No. 4,415,696) compatibility with polycarbonate is also a problem and the waxy, often part-liquid, part-wax, consistency of these products is often a hindrance.
Zwitterionic compounds as polymerization catalysts are known from U.S. Pat. No. 4,927,911. However, nothing is said of their suitability as mold release agents.
Furthermore, JP-A 62 109 854 or DE-A 2 409 412 disclose an anti-static effect of zwitterionic compounds, also in combination with other surface-active compounds. However, their potential suitability as mold release agents was not disclosed.
On the basis of the prior art, the object was therefore to find more effective mold release agents, which are effective at low concentrations, do not produce mold deposits and do not result in haze or discoloration in the effective concentrations, and thus to provide a molding composition which may be de-molded easily and which, besides outstanding de-molding properties and transparency, have adequate temperature stability without discoloration or transesterification.
As a result of the demands for shorter cycle times and higher processing temperatures, combined with the increasing complexity of molds, the immediate de-molding of polycarbonate moldings, retaining the very high-quality surface, is also a constant requirement.
DETAILED DESCRIPTION OF THE INVENTION
The object was achieved by the use of amphoteric zwitterionic substances.
The present invention therefore provides the use of amphoteric zwitterionic substances as mold release agents in thermoplastic molding compositions.
The present invention also provides molding compositions containing 90-99.995 wt. % of a thermoplastic
0.005 to 5.0 wt. %, preferably 0.001 to 2.0 wt. %, in particular 0.01 to 1.0 wt. % of a zwitterionic compound.
The molding compositions according to the invention may also contain conventional additives such as e.g. thermal stabilizers, UV stabilizers, other mold release agents, flame retardants, anti-dripping agents, fillers, glass fibers and blend partners such as ABS, SAN, EPDM or polyesters based on terephthalic acid and diols.
The molding compositions according to the invention may be contaminated with impurities contained in the individual constituents of the molding composition as a result of synthesis, processing, working and storage, and contaminants originating from production or processing of the molding compositions according to the invention. However, the aim is to achieve products that are as clean as possible.
The present application also provides moldings containing the molding compositions according to the invention.
Zwitterionic compounds according to the invention are understood to be compounds in general, which carry at least one positive and at least one negative charge on one charge centre each (for example an atom/a group of atoms) within a molecule. The charge centres are therefore linked to each other by covalent bonds.
Compounds of the formula (I):
R
1
R
2
R
3
—Y
+
—R
4
—X
−
(I)
are preferred.
Wherein
R
1
, R
2
, R
3
independently denote alkyl-, aryl-, alkaryl-, aralkyl group having 1-30 C atoms, un-substituted, or wholly or partially chlorinated or fluorinated optionally also branched, preferably phenol or un-branched, un-substituted alkyl group having 1-20 C atoms, in particular phenyl, methyl or alkyl having 12-20 C atoms most particularly methyl or phenyl,
R
4
denotes bivalent alkylene group having 1-30 C atoms, un-substituted or wholly or partially chlorinated or fluorinated and optionally also branched, preferably un-branched, un-substituted &agr;,&agr;-alkylene group C
1
-C
5
,
Y denotes nitrogen or phosphorus, preferably nitrogen,
X denotes —SO
3
−
, —COO
−
, PO
3
−
, preferably —SO
3
−
.
Sulfobetaines (X=—SO
3
−
and Y=nitrogen) in which at least one of the groups R
1
, R
2
, R
3
represents a linear alkyl group with 12 to 20 C atoms, the remaining groups represent methyl groups and R
4
represents an alkyl group with 2-5 C atoms, are preferred in particular.
N,N-dimethyl-N-stearyl-N-(3-sulfopropyl)-ammonium-betaine (Ralufone® DS, Raschig AG, Ludwigshafen, Germany) is most preferred.
The zwitterionic substances according to the invention are commercially available and may be purchased from well known sources in the chemicals trade.
Thermoplastics according to the invention are understood to be polymers of ethylenically unsaturated monomers and/or polycondensates of bifunctional reactive compounds. Mixtures of several plastics are also possible.
Particularly suitable thermoplastics are polycarbonates or copolycarbonates based on diphenols, poly- or copolyacrylates and poly- or copolymethacrylates such as for example and preferably polymethyl-methacrylate, poly- or copolymers containing styrene, such as for example and preferably transparent polystyrene or polystyrene acrylonitrile (SAN), transparent thermoplastic polyurethanes and polyolefins such as for example and preferably transparent polypropylene types or polyolefins based on cyclical olefins (e.g. TOPAS®, Ticona), poly- or copolycondensates of terephthalic acid, such as for example and preferably poly- or copolyethylene terephthalate (PET or CoPET) or glycol-modified PET (PETG).
Thermoplastic, aromatic polycarbonates or copolycarbonates are preferred in particular.
Thermoplastic, aromatic polycarbonates according to the present invention are both homopolycarbonates and copolycarbonates; the polycarbonates may be linear or branched, in the known way.
A part, up to 80 mol %, preferably 20 mol % to 50 mol % of the carbonate groups in the suitable polycarbonates according to the invention may be replaced by aromatic dicarboxylic acid ester groups. Such polycarbonates, which contain, incorporated into the molecule chain, both acid groups of carbonic acid and acid groups of aromatic dicarboxylic acids, are, to be precise, aromatic polyestercarbonates. For the sake of simplicity, they will be subsumed into the generic term thermoplastic, aromatic polycarbonates in this application.
The polycarbonates to be used according to the invention are produced in the known way from diphenols, carbonic acid derivatives, optionally chain stoppers and optionally branching agents, part of the carbonic acid derivatives being replaced by aromatic dicarboxylic acids or derivatives of dicarboxylic acids t
Döbler Martin
Ebert Wolfgang
Köhler Walter
Neumann Siegfried
Bayer Aktiengesellschaft
Buttner David J.
Gil Joseph C.
Matz Gary F.
Preis Aron
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