CA1262982A - Blending temperature sensitive components into a silicone modified thermoplastic - Google Patents

Abstract

BLENDING TEMPERATURE SENSITIVE COMPONENTS INTO
A SILICONE MODIFIED THERMOPLASTIC

ABSTRACT OF THE DISCLOSURE

A continuous process for incorporating additives into a thermoplastic fluid blend is provided;
said additives typically being sensitive to the tempera-ture at which the blend is produced, said process com-prising the steps of blending a high viscosity silicone fluid and thermoplastic composition initially and feed-ing the additives with more thermoplastic into the extruder for blending.

Description

RD-15,370 BLE~DING TEMPE~ATURE SENSITIVE COMPONENTS INTO
A SILICONE MODIFIED THERMOPLASTIC
Bac~ground of the Invention This invention relates to a method of producing blends of thermoplastic polymers and high viscosity silicone fluids which contain temperature sensitive additives. More particularly, this invention relates to a one-step process for producing a thermoplastic/
silicone fluid blend containing additives sensitive to the blending temperature.
Blending -thermoplastic polymers with silicone fluids often provides blends with desirable enyineering properties and improved flame retardance, such as where the silicone fluid is part of a flame retardant package.
Examples of such desirahle blends are disclosed by McLaury, et al. in U.S. Patent 4,273,691, and by Frye in U.S. Patent 4,387,176; both disclosures being assigned to th~ same assigneeO
Producing thermoplastic/silicone fluid blends with temperature sensitive additives has presented cer-tain problems. The dispersion obtained when blending high viscosity silicone fluids and certain thermoplastic compositions has been found to be directly related to the magnitude of the temperature during blending. The limitation on the magnitude of the blending temperature is typically the temperature at which the thermoplas-tic polymers within the thermoplastic composition degrade.
For such blends there is often an optimum blending RD-15,370 temperature range where a high degree of dispersion is obtained with minimal polymer degradation. ~en blend-ing at these optimum tempera~ures, blends with superior engineering properties are obtained. Often a desirable additive is sensitive to these optimum blending temper-atures. An example of such an additive is the flame retardant aluminum trihydrate. To avoid loss of the additive's properties during blending, the blending temperature must be reduced. As a result, the engin-eering properties of the thermoplastic/silicone Eluid blend suffer.
The present method of avoiding the loss of superior engineering properties and maintaining the integrity of the additive is to blend the high viscos-ity silicone fluid and thermoplastic composition at an optimum blending temperature in the absence of the tem-perature sensitive additive and then subsequently blend in the temperature sensitive additive at a lower temper-ature. This procedure is disadvantaged in that two sep-arate blending procedures are required. ~o produce these thermoplastic/silicone fluid blends continuously, two extruders are required, i.e., twice the equipment required for conventional blending is utilized. Alter-natively, the blend sample may be ~lended within one extruder twice, once at the optimum blending tempera-ture and once with the sensitive additive. Therefore, either tbe rate of production suffers or the equipment required must be increased when sensitive additives are incorporated in the blend.
It is desirable to produce thermoplastic/sil-icone 1uid blends containing additives sensitive to the optimum blending temperatures in a continuous, one-step procedure. The present invention is based on the discovery that the blend may be cooled within the ex-truder by feeding in a solid thermoplastic composition RD 15,370 without significantly affec-ting the dispersion o~
blend constituents.
Summary of the 'Inven*ion A method of continuously producing a thermo-plastic/silicone fluid blend comprising the steps o~:
(a) Blending a high viscosity silicone fluid having a viscosity of at least 90,000 centi-poise at ambient temperature and a primary thermoplastic composition comprising one or more thermoplastic polymers within an extruder at a blending temperature sufficiently high to melt said thermoplastic composltion, the weight ratio of the primary thermoplastic composition to the h.igh viscosity silicone fluid providing a value in the range of 100 to 1;
(b~ Feeding in a manner as to achieve some cooling of the blend of step (a), one or more additives sensitive to said blending temperature with a secondary thermoplastic composition comprising 2Q one or more thermoplastic polymers into said extruder downstream of the point where the bl.ending in step (a) originates, -the weight ratio of the secondary thermoplastic composition and the blend of step (a) providing a value in the range o~ 1 to 0.01; and ~c~ Blending said blend of step (a) with the secondary thermoplastic composition and the additives of step (b~.
Obj'e'c'ts o'f' the' I'n'ven't'ion An object of the present invention is to provide a simple, one~step, continuous process for producing large quantities of thermoplastic/silicone fluid blends containing additive sensitive to the blending temperature.

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RD~lS,370 Another object of the present invention is to produce thermoplastic/silicone fluid blends having ad-ditives sensitive to the blending temperature with im-proved property profiles.
S ~nother object of the present invention is to introduce additives sensitive to the blending tempera-ture of thermoplastic/silicone fluid blends without af fecting the dispersion of the high viscosity silicone fluid.

Description of the Preferred Embodiments _ The objects of the invention and other objects are accomplished by blending a high viscosity silicone fluid and a primary thermoplastic composition comprised substantially of one or more thermoplastic polymers within an extruder and feeding temperature sensitive ad-ditive~ with a secondary thermoplastic composition com-prising one or more thermoplastic polymers downstream of the point where blending between the high viscosity sil-icone fluid and the pximary thermoplastic composition takes place. The additives and secondary composition are then blended with the thermoplastic/silicone fluid blend witllin the extruder.
In the process comprising this invention an extruder is utili~ed to perform the blending steps.
The process does not require a particular extruder or screw geometry to achieve the desired objects. ~ow-e~er, a particular extruder ox screw geometry may be preferred to provide suitable mixing and to avoid exces-sive degradation of the thermoplastic polymers. Twin screw extruders are often preferred for their high shear rates, their distribution of shear rates, ~n~ the ty,oe of agitation applied to the melt.
The blending of the high viscosity silicone fluid and primary thermoplastic composition that occurs .. . . . .. . . . ... . ... . . .. . . .... ... .. . . . . .. . . .

R~-15,370 within the extruder may be carried out in accordance with the process disclosed U.S. Patent 4,446,090 .. ... . .
issued May 1, 1~84 to Lovgren et al wherein t~e primary thermoplastic composition is fed into the feed hopper and melted within an extruder, the high viscosity sili-cone fluid is fed into the molten primary thermoplastic composition within the extruder and said molten primary thermoplastic composition and said high viscosity sil-icone fluid are blended in the remaining portion of the extruder.
The blending of the high viscosity silicone fluid and the primary thermoplastic composition may also be accomplished in accordance with more conventional processes as disclosed in U.S. Patent 4,446,090, ~. . .
l~ issued May l, 1984, wherein ~:he sol~d primary thermo-plastic compositlon and high viscosity silicone fluid are premixed to provide a uniform feedstock suitable for placement within the feed hopper of a conventional extruder. The high viscosity silicone fluid and the primary thermoplastic composition are then heated simul-taneously to a temperature sufficiently high to provide a viscosity for the thermoplastic polymers which allows them to flow and be blended with the high viscosity silicone fluid.
In both blending procedures, the blending temperature is determined by the thermoplastic polymers within the primary thermoplastic composition. The blending temperature must be sufficiently high to melt the pr~mary thermoplastic composition. Suitable blend-ing temperatures for primary thermoplastic compositions containing amorphous polymers typically fall within the range having a minimum value of about 7 0 to 80 degrees above the glass transition temperature of the polymer and the maximum ~alue of about the temperature where degradation result~. Where ~he primary thermoplastic . . . .. .. .. . . , . , . . . , . , , , , ~ , . .. .. .

~lZ~
RD-15,370 composition contains crystalline polymers sultable tem-pexatures fall within the range having a minimum value of about 20 to 30 degrees above the crystalline meltin~
point of said polymers and a maximum value of about the degradation temperature of said polymers.
The extent of dispersion of a high viscosity silicone 1uid within the primary thermoplastic compo-sition during blending is dependent on the processing temperature at which blending takes place. Therefore, when attempting to maximize the dispersion of blend constituents in thermoplastic/silicone fluid blends, the blending temperature is adjusted to provide maximum dispersion. Often the degree of dispersion obtained in-creases with temperature. In such a situation, the op-timum blending temperature range may approach the degradation temperature of the polymers within the primary thermoplastic composition. However, even at these t~mperatures maximum dispersion is ob-tained with zero or minimal polymer degradation.
Once the primary thermoplastic composition and high viscosity silicvne fluid are blended at a blending temperature within the range defined above, the temper-ature sensitive additives which are desired in t~e fin-ished blend are introduced into the extruder with a secondary thermoplastic composition comprising one or more thermoplastic polymers. The quantity of secondary thermoplastic polymer is preferably large enough to re-duce the heat of the molten blend within the extruder to a point where the temperature sensitive additives will not be affected. By introducing solid thermoplastic polymer into the hot blend, sensible heat of the blend is consumed as the temperature o~ the solid thermoplas-tic increases to the process temperature. Where the solid ~hermoplastic polymer is crys~allin~, an addi~
tional amount of heat, the heat of fusion, which is required to melt the polymer is also consumed.

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RD-15,370 The temperature sensitive additives and the secondary thermoplastic composition can be fed anywhere along the extruder provided it is downstream of the point where blending of the high viscosity silicone fluid and primary thermoplastic composition initiates.
It is preferable to introduce the additives and second-æy thermoplastic composition at a point on the extruder where the desired dispersion has been obtained within the blend. This point can vary depending on the ex-trudex and on the blending process. For example,where the blending is achieved by a side feed process, as diqclosed in U.S. Patent Number 4,446,090, issued May l, 1984,'`adequate blending may not be obtained be-fore ~he mid~point of the extruder, since no blending takes place in the extruder until the silicone is in-jected. ~here a twin screw extruder is utilized, it is preferable to feed the additives and solid secondary thermoplastic composition at a point about Z/3 the ex-truder length froM the feed hopper. This ensures that the secondary thermoplastic composition is dispersed within the blend and that blending between the high viscosity silicone ~luid and primary thermoplastic composition is adequate.
The de~ree of agitation necessary to ~lend the secondary thermoplastic composition into the molten blend within the extruder is not as high as that re-quired to initially disperse the high viscosity sili-oone fluid into the primary thermoplastic composition.
~ere the secondary thermoplastic composition and the primary thermoplastic composition are similar, the de-gree of agitation that is necessary is even less.
The secondary thermoplastic composition may be ~ed slmultaneously with the temperature sensitive additives or it may be fed before the additives so as to cool dow~ ~he blend within the extruder prior to .. ... . . .. .. . .. .. . . . . .... . . ... ... . ..... . . .. . . ... . . .. .. .. . . . ..

~2629~% ~D-15,370 introduction of the additives. As indicated above, the secondary thermoplastic composition mus-t be introduced downstream of the point where blending between the high viscosity silicone and primary thermoplastic com-position is initiated. It is preferable to introducethe secondary thermoplastic composition subsequent to obtaining the desi~ed dispersion of high viscosity silicone within the primary thermoplastic composition.
Once the secondary thermoplastic composition and temperature sensitive additives are introduced into the extruder, they are blended with the thermoplastic/
silicone fluid blend within the extruder. Preferably, this ~lending procedure takes place at a temperature which does not antagonize the additives introduced.
Typically, this temperature is belsw the blending tem-perature utilized to blend the high viscosity silicone fluid and the primary thermopl~astic composition. The blending temperature must be sufficiently high to main-tain the viscosity of the polymers within the primary thermoplastic composition and the secondary thermoplastic compositic,l at a value that permi-ts them to flow and be blended with other constituents. Minimum temperatures for the polym~rs in the secondary composition are the same as for those in the primary thermoplastic compo-sition.
The weight ratio of the primary thermoplasticcomposition to the high viscosity silicone fluid prefer-ably provides a value in the range of 100 to 1. Most preferably the value of such a ratio falls in the range of about 5 to about 2. It is often preferable to pro-duce a blend which is predominantly thermoplastic poly-mer in the initial blending s~ep to reduce the agitation which is necessary to disperse the secondary thermoplas-tic composition.

....... . . . . .... . . . . .. . . . . .... ..... ... ..... . . . .
.. ...

Rb-15,370 Preferably, the quantity of thermoplastic polymers utilized in the secondary thermoplastic compo-sition is sufficiently high to cool the blend within the extruder to a temperature that permits the addi-tives to be introduced without any harmful effect.
Therefore, the quantity of thermoplastic polymer util-ized typically falls within the range of about 50~ to about 1% of ~he total weight of ~he high viscosity 5il-icone fluid and the primary thermoplastic composition blended within the extruder. However, the quantity of thermoplastic polymers within the secondary thermoplas-tic composition must not be so high as to prevent ade-quate mixing in the remaining portion of the extruder.
Thermoplastic polymers which are suitable for use in this process include, for example, polycarbon-ates, low density polyethylenes, high density poly-ethylenes, polypropylene, polyphenylene ethers, poly (alkyleneterephthalates), polystyrene, polyesters, acrylonitrile, butydiene, styrene, polyethylene ethers-polystyrene blends and copolymers, polybutylene, poly-caprolactans, etc. Suitable acrylic polymers include acetyl, ethylene, vinyl acetate, polymethyl-pentene, ~lex.ible polyvinyl-chloride, etc. It is not intended that the above listing be all inclusive.
The h.igh viscosity silicone fluids are prin-cipally comprised of high molecular weight silox~ne polymers having viscosity values in the range of 90,000 centipoise and above at ambient temperature. The siloxane polymers are tYpically compxised of chemically co~.bined siloxy units selected from the group consist-ing of:
R3Sioo 5 RR'SiO
R2 Sio . R'~SiO

. . .... .....

z RD-15,370 RiSiOl 5 ~SiOl 5 R'R2SiOo 5 and SiO2 units, wherein each R represents a saturated and unsaturated monovalent hydrocarbon radical, R' represents a radical such as R or a radical selected ~rom the group consist-- ing of a hydrogen atom, hydroxy, alkoxyaryl, alyl, vinyl, aryl radical, etc. A preferred siloxane polymer is polydimethylsiloxane having a viscosity of about 90,000 to 1,500,000 centipoise at 25 Centigrade.
Other constituents which may be found in the high visc05ity silicone fluids include silicone resins as defined by Frye in U.S. Patent 4,387,176. These are typically characterized by the monomers within them.
For example, MQ resins are comprised oE M units of the formula R3SiOo 5 and tetrafunctional ~ units of the foxmula SiO2. An example of a suitable MQ silicone resin is polytrimethylsilylsilicate, which can have a ratio of M to Q units providing a value range of 0.3 to ~Ø Silicone resins containing other units such as the trifunctional uni~ R~iOl 5, are also suitabl~. ~here a silicone resin is utilized in the high viscosity sili-cone ~luid a criteria for suitability is that each sill-cone resin be soluble or dispersable within the mixture of high molecular weight siloxane polymers that are pre~ent so as to provide a homogeneous mixture. It is preferable to premix the silicone resins and the siloxane pol~mers prior to blending with the primary thermoplastic composition within the extruder.
The preferred high viscosity silicone fluids are those disclosed by Frye in U.S. Patent 4,387,176.
These silicone fluids typically contain a mixture of high molecular weight siloxane polymers and one or more silicone resins. An example of a high viscosity sili-cone fluid disclosed by Frye is a mixture containing a , . . . . . , . . . ... . .. ... . . . . . .. .. . .. . .. . , ~ . ., . , . .... . , , . . . .... ~ .
.. . .... .... .

RD-15,37~

silanol stopped polydimethylsiloxane pol~mer and poly-trimethylsilylsilicate MQ resin.
The blend constituents which are added subse-quent to the blending of the high viscosity silicone fluid and the primary thermoplastic composition are typ-ically sensitive to high temperatures. An example of such a blend constituent is aluminu~ trihydrate. This additive offers flame retardance to thermoplastic com-positions by dehydrating when exposed to heat of the combustion process. I~ exposed to high processing tem-peratures, aluminum trihydrate can dehydrate in the extruder and i~s flame retardance mechanism is lost.
Although this process is useful for introduc-ing additives which are sensitive to the blending tem-perature, additives which are insensitive to the blend-ing temperature can a]so be introduced to the blend.
These additives may include, for example, re-- inforcing fillers, cross-linking agentsl antioxidants, lubricants (processing aids), flame retardants, etc.
Where the additives are insensitive to the processing temperatures, they are often apportioned between the molten thermoplAstic composition and the silicone fluid when produced by a side fed operation~ Where the blends are produced by a conventional continuous process, the additives axe introduced into the feed hopper with the pre-mixed high viscosity silicone fluid and primary thermoplastic composition. Suitable additives which can be found in the finished blend include those dis-closed by Frye in U.S. Patent 4,387,176. These more particularly include Group IIA metal organic compounds or salts, such as magnesium stearate, calcium steaxate, barium stearate, etc., which enhance the flame retaxd-ance of the thermoplastic/silicone fluid blend. Other flame retardants include the more conventional mater-ials, such as antimony oxide and decabromodiphenyl , . 11 .... .... . ..

~-15,370 oxide. Cross linking agents, such asdi~umyl peroxide and primary reinforcing fillers, such as fume silica, clay, talc,wollastonite,calcium carbonate, aluminum tri hydrate, etc. can be fed into the feed hopper with the solid prImary thermoplastic compositionO
When producing blends of polypropylene and high viscosity silicone fluids having additives sensi-tive to the blending temperature, the polypropylene is preferably preblended with the desired additives which are insensitive to the blending temperature where these blends are produced by the side fed process disclosed ln U.S. Pa-t. 4,446,090. These typically include, for e~-ample, cross linking agents, reinforcing fillers, anti-oxidants and processing aids.
The polypropylene and silicone fluid are typ-ically blended at a temperature within the range o~
about 200 to 300 Centigrade, the preferred blending temperature falling within the range of about 210 to 230 Centigrade~ Under these conditions, at most only minor polypropylene degradation results and the dis-persion of the high viscosity silicone fluid is suffi-ciently high to provide excellent enyineering properties (Impact resistance, tensile str~ngth, etc.).
An example of a desired constituent which is sensitive to the pre~erred processing temperature range of 210 to 230 Centigrade is aluminum rihydrate. This additive dehydrates at these temperatures resulting in a loss of its flame retardant capabilities. Although other flame retardants are insensitive to such optimum blending temperatures, aluminum trihydrate has been found to offer improved flame retardance tG polypropy-lene/silicone fluid blends when produced by this pro-cess. Such blends typically exhibit short average burn times of 5 seconds or less after exposure to a flame test in accordance with Underwriters Laboratories, In-corporated Bulletin UL-94.

.. . ... . .. .. .. . . ... . .

RD-15,370 The aluminum trihydrate is preferably intro-duced into the extruder with additional polypropylene, the quantity of polypropylene ranging from 1% to lOG~
by weight of the polypropylene/silicone fluid blend pro-duced within the extruder. Most pre~erably, the quan-tity of polypropylene is sufficiently high to reduce the temperature o~ the thermoplastic/silicone fluid blend within the extruder to a temperature within the range of about 180 to 200 Centigrade. The tempera-ture of the polypropylene not only cools the blend byconsuming sensible heat, it also cools the blend by consuming the heat of fusion necessary to melt the solid crystalline polymer.
The point of injection of the aluminum tri-hydrate and polypropylene is about one~half to two-thirds the extruder length from the feed hopper, the point of injection being independent of the type of process utilized to produce the thermoplastic/silicone fluid blend. The preferred quantity of aluminum tri-hydrate typically falls within the range of 0.1% to5% by weight of the finished blend.
The thermoplastic polymers utilized in the secondary thermoplastic composition may be the same as, but are not limited to the thermoplastic utilized in the primaxy composition. When producing thermoplastic/
silicone fluid blends containing polyphenylene ether, polystyrene and a high viscosity silicone fluid, poly-phenylene ~ther may principally comprise the primary thermoplastic composition and polypropylene ~ay prin-cipally comprise the secondary composition, The following examples are provided in orderthat thosP skilled in the art may be better able to understand this invention. They are provided to illus-trate this invention and are not intended to ~Lmit the scope of this invention.

... . ...... " .. ..................... . .. . . .. .. ... . . .. .. ... . .... . ..... . ..... .. ... .... .. . . .. . .

t~ 2 RD-15,370 Exam~le I
A polypropylene/silicone fluid blend was produced utilizing Werner and Pfleiderer Model ZSK-30 co-rotating twin -i ~ screw extruder with intensive mixing screws 30 mm in diameter and 29 diameters in length. A fu11y formulated blend was produced in a single pass, said blend comprising 57.7 parts by weight polypropylene, 8.5 par~s by weight high viscosity silicone ~luid (comprising polydimethyl-siloxane and MQ resin in a ratio having a value within the range of 1.9 to 1.0), 4.0 parts by weight magnesium stearate~ 18.8 parts by weight aluminum trihydrate ~ATH) flame retardant and the remaining portion being decabromo-diphenyl oxide.
The side ~eed process described in U.S. Patent Number 4,446,090, issued May 1, 1984 was utilized~ l~e pc~lypropylene magnesium stearate, aluminum trihydrate and decabromodiphenyl-oxide were introduced to the twin screw extruder through the feed hopper. The polypropylene was melted within the extruder and the silicone fluid was fed into the extruder at a point 1/3 of the extruder length from the feedhopper. The high viscosity s;licone fluid and the molten thermoplastic composition were blended at various melt temperatures, including 188C, 198C, 2n40c and 215C ~t a scre~ speed of 300 RPM and throughput rate of 20 lbs/hr.
Four additional samples were run at a screw speed of 500 RPM and throughput rate of 20 lbs/hr. at the temperatures indicated above.
The burn times for the eight blends are shown in Table I. The burn times were taken in accordance with the test described in Underwriters Laboratories, Inc. Bulletin UoL~~94 Table I
Melt temperature 188C 198C 204C 215C
Burn times (sec) 15 5 3.5 9 300 RPM screw speed Burn times (sec) 18 7 5 6 500 RPM screw speed . .

.. . . . ... ., .. .. .~ . .

~ B~ RD-l5,370 Example II
This example demonstrates embodiments of this invention where the inte~rity of the blend constitutents that are sensitive to the blending temperature of the high viscosity silicone fluid and thermoplastic composi~ion is maintained. The blend samples produced in this example had a similar composition to those produced in ~xamp?e I, i.e. 57.7 parts by weight of polypropylene, 8.5 parts by weight high viscosity silicone fluid (polydimethyl-siloxane and MQ resin), 4.0 parts by weight magnesium stearate, 18.8 parts by weight aluminum trihydrate (ATH) flame retardant and the remaining portion being decabromodiphenyl oxide.
The same co-rota~ing twin screw extruder was utilized and the side fed process disclosed in u.s. Patent 4,446,090 issued~ay 1`, 1984 was utilized to pro~uce the silicone ~ , .. ,.. , ~ ~
lS fluid/primary thermoplastic composition blend. The polypropylene magnesium stearate and decabromodiphenyl oxide were introduced into the feedhopper of the co rotating twin screw extruder, the polypropylene being in an amount of 5Z weight percent of the ~inished blend. The polypropylene was melted within the extruder and the high viscosity silicone fluid was introduced to the extruder at a psint about l/3 the extruder length from the feedhopper.
Three polypropylene/silicone fluid blends were produced at melt temperatures of about 200C, 205C; and 210C,respectively, and a screw speed of 500 RPM within the extruder. The ATH was fed with a portion of polypropylene, (5.7 weight percent of the finished bl~nd) into the three blends downstream of the silicon iniection part and blended in the extruder. The burn times for three blends were taken in accordance with the test disclosed in Bulletin U.L.-94 and are indicated in Table II along with the engineering properties of the blends.
Table II
Melt temperatures 200C 205C 210O
Burn times (sec) 3.8 3.8 3.4 Tensile strength ~psi) 34lO 3412 3420 Gardner ;mpact ~in. lbs.) 148 165 184 , .... ... ... .... .

6 ~ ~ RD~15,370 Example_III
This example demonstrates an alternative procedure where po1ypropylene is not introduced with the ATH. The same three blends were produced atd~fferent melt temperatures than Example IIg howeuer, all the polypropylene was introduced into the feed-hoppPr and the ATH was fed into the extruder downstream of the silicone injection part without polypropylene.
The burn ti~es for the blends produced were taken in accordance with the flamability test described in Bulletin U.L.-94.
1.0 The burn ~imes and engineering properties appear in Table III.
Table III
Melt te~peratures 190C 210C 220C
Burn times (sec) 15 7 9 Tensile strength (psi) 3450 344~ 3465 lS Gardner Impact (in lbs.) 1 zn 50 160 The data in Table III illustrates the erratic burn times obtained by this process indicating dehydration of ATH results.
Although the above examples have shown various modifications of the present invention, further modi~i-cations are possible in light of the above teaching byone skilled in the art without departin~ ~rom the spiri~ and scope o~ ~he inventi~n.

. 16 .

Claims (15)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of continuously producing a thermoplastic/silicone fluid blend comprising:
(a) blending a high viscosity silicone fluid having a viscosity of at least 90,000 centipoise at ambient temperature and a primary thermoplastic composition comprising one or more thermoplastic polymers within an extruder at a blending temperature sufficient high to melt said primary thermoplastic composition, the weight ratio of said primary thermoplastic composition to said high viscosity silicone fluid providing a value in the range of 100 to 1;
(b) feeding in a manner as to achieve some cooling of the blend of step (a), one or more additives sensitive to said blending temperature with a secondary thermoplastic composition comprising one or more solid thermoplastic polymers into said extruder downstream of the point where the blending in step (a) originates, the weight ratio of the secondary thermoplastic composition and the blend of step (a) providing a value in the range of 1 to 0.01; and (c) blending said blend of step (a) with the secondary thermoplastic composition and the additives of step (b).

2. A method as in claim 1 wherein the primary thermoplastic composition and the secondary thermoplastic composition are comprised of the same constituents.

3. A method as in claim 2 wherein the thermoplastic compositions are comprised essentially of one or more thermoplastics selected from the group consisting of polycarbonates, low density polyethylenes, high density polyethylenes, polypropylene, polyphenylene ethers, poly(alkylene terephthalates, polystyrene, polyesters, polyamides, polyimides, polyurethanes, terpolymers of acrylonitriles, butadiene and styrene.

4. A method as in claim 3 wherein the thermoplastic compositions contain 1 to 3% filler selected from the group consisting of talc, clay, fumed silica, calcium carbonate, and wollastonite; and 5 to 10% cross-linking agent selected from the group consisting of dicumyl peroxide.

5. A method as in claim 4 wherein the primary thermoplastic composition and the secondary thermoplastic composition consist essentially of polypropylene.

6. A method as in claim 1 wherein the high viscosity silicone fluid is comprised of 20 to 100% of polysiloxane polymers having an average molecular weight of 50,000 and above and 2 to 40% of an MQ
silicone resin wherein the M units are of the formula R3SiO0.5 and the Q units are of the formula SiO2 where R represents a saturated or unsaturated monovalent hydrocarbon radical.

7. A method as in claim 6 wherein said high viscosity silicone fluid is comprised of about 40 to 100% polydimethylsiloxane.

8. A method as in claim 7 wherein the high viscosity silicone fluid contains 2 to 50% MQ silicone resin wherein the ratio of M units to Q units falls within the range of 0.3 to 4Ø

9. A method as in claim 5 wherein the high viscosity silicone fluid and the polypropylene are blended at a temperature falling within the range of 200°C to 230°C.

10. A method as in claim 9 wherein the blending temperature falls within the range of about 210°C to 230°C.

11. A method as in claim 10 wherein the temperature sensitive additive is principally comprised of aluminum, trihydrate.

12. A method as in claim 11 wherein the ratio of high viscosity silicone fluid to the primary thermoplastic composition is four to one and the ratio of the secondary composition to the blend of step (a) is within the range of 1 to 0.05.

13. A method of continuously producing a polypropylene/silicone fluid blend comprising:
(a) blending a high viscosity silicone fluid having a viscosity of at least 90,000 centipoise at ambient temperature and a composition comprised substantially of polypropylene within an extruder at a temperature within the range of about 210°C to 230°C, the weight ratio of polypropylene to the high viscosity silicone fluid providing a value within the range of about four to one;
(b) feeding aluminum trihydrate with polypropylene into an extruder downstream of the point where the blending in step (a) originates, said feeding is in a manner as to achieve some cooling of the blend of step (a), the weight ratio of the blend of step (a) and the secondary portion of polypropylene providing a ratio of about 100 to 1; and (c) blending said blend of step (a) with the secondary portion of polypropylene and the aluminum trihydrate.

14. A method as in claim 13 wherein the high viscosity silicone fluid is comprised of 20 to 100% polydimethylsiloxane and 2 to 40% MQ silicone resin wherein the ratio of the M units to Q units fall in the range of about 0.03 to 4Ø

15. A polypropylene/silicone fluid blend containing aluminum trihydrate produced in accordance with the process of claim 14, said blend comprising:
(a) 40 to 80% polypropylene;
(b) 20 to 40% polydimethylsiloxane;
(c) 5 to 20% MQ resin, wherein the ratio of M to Q units is within the range of 0.03 to 4.0;
(d) 1% to 18% aluminum trihydrate;
(e) 0 to 10% talc; and (f) 0 to 15% cross-linking agent selected from the group consisting of dicumylperoxide and decabromyldiphenyloxide.