Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-02-16
2002-10-15
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S216000, C525S232000, C525S240000, C525S241000
Reexamination Certificate
active
06465574
ABSTRACT:
The present invention relates to a process for preparing moulded articles by powder moulding. It also relates to polyolefin compositions, in particular heterophasic polyolefin compositions, suitable for preparing said articles and to the moulded articles thus obtained.
The term powder moulding is used in broad sense in the present application, to embrace processes where moulded articles (in particular, laminar or hollow articles) are obtained by deposition of polymer powders on the inside wall of a mould and by melting such powders in contact with the mould in one or more steps. Therefore, such term includes slush moulding and other known processes, such as the rotary moulding process.
Thanks to the particular polyolefin composition used in the process of the present invention, the said process is particularly suitable for producing laminar articles with a complex shape.
Thermoplastic elastomeric polyolefin compositions have already been used in slush moulding processes. Hence, thanks to the use of said compositions, laminar articles with a high degree of softness are already available.
European patent applications No. 637610 and No. 97/952761.1 (WO 98/21273) describe said process and articles. However, the compositions used in the process described in the above-mentioned patent applications are suited for producing articles with a simple shape only. In fact, the demoulding of an article with complex shape is difficult because of the relative stiffness of the said compositions.
Moreover, when an industrial plant is used for carrying out the process described in the said patent applications, it is necessary to heat the mould to high temperatures, i.e. at least to 250° C., in order to sinter the polymer powder.
It has now been found that moulded articles (for instance synthetic leathers) having a good degree of softness even in the absence of extender oil, soft touch and good mechanical properties can be obtained by using powders of particular polyolefin compositions, without incurring difficulties in the demoulding step.
Moreover, thanks to the particular type of polymer composition it is now possible to heat the mould of an industrial plant to temperatures lower than usual, i.e. temperatures of less than 250° C. Lower temperatures are a great advantage because they allow to shorten the cycle time, thereby increasing the productivity. Moreover, less energy is required in order to heat the mould.
As said above, an example of laminar articles obtainable with the process of the present invention are synthetic leathers. For example, synthetic leathers are used in the automotive industry vehicle parts. The synthetic leather of the present invention can be used to cover dashboards and handles, for instance.
Therefore, the present invention provides a process for the manufacture of a moulded article comprising the powder moulding of a polymer composition having a Shore D hardness value of less than 40 points, preferably from 70 Shore A points to 35 Shore D points, according to method ASTM D 2240, said polymer composition comprising:
1) a polyolefin composition consisting of:
i) 5 to less than 100, such as 5 to 95, preferably 20-70, most preferably 20-50, parts by weight of a crystalline or partially crystalline isotactic polymer of 1-butene; and
ii) more than 0 to 95, such as 5 to 95, preferably 30-80, most preferably 50-80, parts by weight of a thermoplastic elastomeric polyolefin composition having a melt flow rate of 20-100 g/10 min (at 230° C. and 2.16 kg); or
2) a polyolefin composition consisting of:
iii) 100 parts by weight of a crystalline or partially crystalline isotactic polymer of 1-butene or composition (1); and
iv) more than 0 to 100, such as 3 to 100, preferably 5-100, parts by weight of an elastomeric polymer;
with the proviso that when the polymer of 1-butene is a homopolymer or a copolymer with less than 2% by weight of comonomer, polymer compositions (1) and (2) contain at least 5, preferably at least 10, parts by weight of an elastomeric polymer.
The said elastomeric polymer can be either polymer (iv) or the elastomeric polymeric fraction of the thermoplastic elastomeric composition (ii).
Generally, the melt flow rate (MFR) value (according to ASTM D 1238, condition L, MFRL) of the above mentioned polymer composition to be used in the process of the present invention ranges from 20 to 100 g/10 min.
Said crystalline or partially crystalline polymer of 1-butene suitable for use in the present invention is selected from both the homopolymers and copolymers of butene-1. In the copolymers, the comonomers are preferably selected from ethylene and C
3
-C
10
&agr;-olefins of formula CH
2
═CHR, where R is a C
1
-C
8
linear or branched alkyl radical, such as propylene and pentene-1. The preferred comonomers are ethylene and propylene. The amount of comonomer is generally from 0.5 to 50%, preferably from 2 to 10%, by weight. Suitable examples are copolymers of butene-1 with 2 wt. % to 6 wt. % ethylene.
The polymers of butene-1 typically have an MFR value varying from 5 to 100 g/10 min (at 190° C. and 2.16 kg).
Said 1-butene polymers are commercially available and can be obtained using known polymerisation processes and catalysts. The polymerisation of 1-butene, optionally in the presence of an olefin comonomer such as ethylene or propylene, can be carried out using Ziegler-Natta or metallocene catalysts. Specific examples of said catalysts are the catalytic systems described in European patent applications EP-A-45977 and EP-A-361494, and the catalytic systems containing metallocene catalysts described in U.S. Pat. No. 476,951. Examples of preparation of polymers of 1-butene are disclosed in U.S. Pat. Nos. 2,882,263, 3,362,940 and 3,112,300.
The thermoplastic elastomeric polyolefin composition (ii) comprises a crystalline propylene polymer and ethylene-propylene rubber, for example. In such a case, the total amount of copolymerized ethylene may be from 15 to 60% by weight.
A suitable example of composition (ii) is a thermoplastic elastomeric polyolefin composition (I) comprising (parts and percentages by weight):
a) 10-40 parts, preferably 20-40, of an isotactic propylene homopolymer having a content of fraction soluble in xylene at room temperature greater than 80%, preferably greater than 90%, or a propylene random copolymer with at least one comonomer selected from ethylene and C
4
-C
10
&agr;-olefins of formula CH
2
═CHR, where R is a C
2
-C
8
linear or branched alkyl radical, said copolymer containing greater than 80% of propylene and having accountant of fraction soluble in xylene at room temperature greater than 80%, preferably greater than 90%;
b) 0-20 parts of a copolymer containing ethylene, insoluble in xylene at room temperature; and
c) 40-95 parts, preferably 40-80, of an elastomeric polymer fraction consisting of a copolymer of ethylene with at least one comonomer selected from C
3
-C
10
&agr;-olefins of formula CH
2
═CHR, where R is a C
1
-C
8
linear or branched alkyl radical, and optionally with a small quantity of diene, said polymer being soluble in xylene at room temperature, having an intrinsic viscosity ranging from 1 to 4 dl/g and containing ethylene in quantities of less than 40%, preferably 15 to 38%, more preferably 15-35%.
For room temperature, a temperature of about 23° C. is meant.
Examples of the above-mentioned thermoplastic elastomeric polyolefin composition (I)are described in European patent application EP-A-0 472 946.
The copolymer constituting fraction (b) may be rich in the said C
3
-C
10
&agr;-olefins or may be an essentially linear copolymer of ethylene with the said C
3
-C
10
&agr;-olefins, such as linear low density polyethylene (LLDPE), for example.
When fraction (b) is present, it is preferable that the quantity of the said fraction be greater than 1 part by weight.
Whenever present, the quantity of diene in said fraction (c) generally ranges from 0.5 to 10% by weight, preferably from 1 to 4%, with respect to the total weight of fraction (c). Specific examples of the said dienes are 1,3-butadiene, 1,4-hexadiene,
Koehler Rainer
Mulas Carlo
Basell Poliolefine Italia S.p.A.
Nutter Nathan M.
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