|JP2001278991||BLOW MOLDED PRODUCT WITH LOW GLOSS|
|WO/1994/018001||THERMOPLASTIC OLEFINIC COMPOSITIONS|
|JP2000169643||TALC-REINFORCED POLYPROPYLENE MOLDING MATERIAL HAVING HIGH IMPACT STRENGTH|
|1.||An impact and weather resistant rubber modifiεd moldablε thermoplastic resin comprising: (a) a hard matrix polymer comprising at least one polymer selected from the group of: polystyrene; polymethylmεthacrylatε; an addition polymer of two or more monomers selεctεd from the group consisting of styrene, acrylonitrile, αmεthylstyrεnε and mεthylmεthacrylatε; and mixtures therεof; and (b) a graftεd alkylacrylatε rubber comprising a rubber having a core of a substantially uncrosslinked alkylacrylate polymer having a Tg less than about 0°C, a swelling index in methyl ethyl ketonε of grεatεr than about 15, a gεl content in methyl ethyl kεtonε of lεss than about 85 weight percent, and a graftable overpolymεr layεr of a high crosslink dεnsity alkylacrylatε polymer, said rubber having grafted therεto at lεast onε polymεr sεlected from thε group of polystyrene; polymethylmethacrylate, an addition polymer of two or more monomers selεctεd from the group consisting. of styrεnε, αmεthylstyrεnε, acrylonitrilε and mεthylmεthacrylate; and mixtures therεof.|
|2.||A thermoplastic resin according to Claim 1, wherein the hard matrix polymεr is a copolymer of styrene and acrylonitrile.|
|3.||A thermoplastic resin according to Claim 1, wherein the rubber core comprises a homopolymer of butylacrylate and has a gel content of less than 65 weight percent and a swelling index grεatεr than 35; and component (b) is present in an amount of from 5 to 30 weight pεrcεnt basεd on thε total wεight of thε moldablε rεsin.|
|4.||A thεrmoplastic rεsin according to Claim 1, 0 wherein the graftable overpolymer layer contains from 01 to 10 weight percεnt of onε or more polymεrlzεd graftlinking or crosslinking monomers.|
|5.||A thermoplastic resin according to Claim 4, 5 wherein the graftlinking or crosslinking monomer is allylacrylate, allylmεthacrylate or diallyl aleatε.|
|6.||A thermoplastic resin according to Claim 1, wherεin the grafted alkylacrylate rubber has a 0 copolymer of styrenε and acrylonitrile grafted therεto.|
|7.||A thεrmoplastic rεsin according to Claim 1 additionally comprising an EPDM rubbεr εlastomεr.|
|9.||A thεrmoplastic rεsin according to Claim 1 additionally comprising a crosslinkεd and graftεd acrylate elastomεr.|
|10.||Thε rεsin of Claim 1 which is capable of 0 being molded into an article having a 60° Gardner Gloss of lεss than 60 when molded on a 2 oz. Nεgri Bossi injεction molding machine at a barrel temperature of 425/450°F and a moid temoeraturε of 110°F.|
|11.||The rεsin of Claim 9 which is capablε of being moldεd into an article having a 60° Gardner Gloss of less than 30.|
|12.||The rεsin of Claim 10 whεrεin thε moldεd resin has a Notched Izod greater than 5 ftlbs/inch notch as measured by ASTM D256.|
|13.||A process for prεparing a molded article having a 60° Gardner Gloss of less than 60, which comprises molding the resin of Claim 1.|
The present invention relates broadly to the preparation of molded resins that have low gloss. It also relates to an impact and weather resistant thermoplastic molding material comprising a blend of a polyacrylate rubber graft copolymer and a compatible rigid phase. More particularly, the present invention relates to such an impact and weather resistant thermoplastic molding material, wherein the polyacrylate rubber grafting ba_e comprises a low gel, high swelling index butylacrylate rubber grafted with a rigid phase polymer.
Articles prepared from molded resins may be classified as having "high gloss" or "low gloss" according to whether their 60° Gardner gloss is above a ' value of 80 or below a value of 60. Most end use applications require either a high gloss or else a low gloss below 30, rather than a gloss in the intermediate range of 31 to 79. In addition, it is well known that it is desirable to obtain the appropriate gloss level without ad v ersely affecting other desirable physical properties.
It is previously known to prepare acrylate rubber polymers comprising homopolymers and copolymers of at least one alkyl acrylate having grafted thereto a suitable rigid phase. Preferred acryϊate rubber particles comprise homopolymers of butylacrylate grafted with homopolymers of styrene or methylmethacrylate or copolymers of styrene with methylmethacrylate or acrylonitrile or both methylmethacrylate and acrylonitrile. Previously known weatherable resins modified by addition of the aforementioned butylacrylate containing rubbers have provided good physical properties and weather resistance, but generally have resulted in medium to high gloss articles under typical injection molding or extrusion conditions. For many applications, such as the interiors of automobiles and the like, it would be desirable to provide a weather rεsi.stant resin having a low gloss or "satin" surface appearance. Accordingly, it is to the attainment of this purpose, that the present invention is directed.
The preparation of impact resistant thermo¬ plastic materials by mixing a "hard" component (a), comprising a copolymer styrene and acrylonitrile, with a "soft" component (b), comprising a graft copolymer of a styrene/acrylonitrile mixture onto a polyacrylate, has been disclosed in GB 1,124,911. Such molding materials are generically referred to as ASA polymers.
Numerous modifications and improvements in such
ASA polymers have been developed. Suitable processes for the preparation of such improved ASA materials include those disclosed in U.S. Patents 4,442,263; 4,456,734; 3,830,δ7S; and 3,561,994. The teachings of
the above described United States Patents are herein incorporated in their entirety by reference thereto.
According to one broad aspect of the present invention, there is now provided an im_act and weather resistant rubber-modified moldable thermoplastic resin comprising: (a) a hard matrix polymer comprising at least one polymerselected from the group of: polystyrene; polymethylmethacrylate; an addition polymer of two or more monomers selected from the group consisting of styrene, acrylonitrile, α-methylstyrene and methylmethacrylate; and mixtures thereof; and (b) a grafted alkylacrylate rubber comprising a rubber having a core of a substantially uncrosslinked alkylacrylate polymer having a Tg less than about 0°C, a swelling index in methyl ethyl ketone of greater than about 15, a gel content in methyl ethyl ketone of less than about 85 weight percent, and a graftable overpolymer layer of a high crosslink density alkylacrylate polymer, said rubber having grafted thereto at least one polymer selected from the g oup of polystyrene; polymethylmethacrylate, an addition polymer of two or more monomers selected from the group consisting of styrene, α-methylstyrene, acrylonitrile and methylmethacrylate; and mixtures thereof. It is preferred that component (b) be present in an amount of from 5 to 30 weight percent based on the total weight of the molding resin. It is also preferred that the gel content be less than 65 weight percent, and the swelling index be greater than 35.
In a second broad aspect of the invention there is provided a orocess for preparing a molded article
having a 60° Gardner gloss of less than 60, which comprises molding the aforementioned resin.
The hard matrix polymer component of the _. present invented thermoplastic resins are well known to the skilled artisan. Preferred hard polymers are those well known thermoplastic resins used in injection molded applications. A particular preferred hard matrix polymer is styrene/acrylonitrile copolymer. The 10 hard matrix polymer may be prepared by any suitable polymerization technique including emulsion, mass, solution, or suspension polymerization techniques, or a combination thereof.
15 The grafted alkyl acrylate rubber is suitably prepared by emulsion polymerization techniques utilizing equipment and processing conditions well known to the skilled artisan. The core rubber is first prepared by polymerizing a suitable alkyl acrylate,
20 optionally In combination with a minor amount, i.e., up to about 20 percent by weight of a copolymerizable comonomer. Suitable alkyl acrylate monomers include the C-|_8 alkyl acrylates. A particularly preferred
-_- alkyl acrylate monomer is butyl acrylate. Suitable copolymerizable comonomers include ethylεnically unsaturated carboxylic acids and esters thereof having from 3 to 10 carbons and monovinylidene aromatic monomers. Preferably, the core consists essentially of
30 polymerized alkyl acrylate monomer.
In the emulsion polymerization, a suitable seed latex may be employed to achieve uniform latex particle size. Such seed latexes preferably are alkyl acrylate 35 homopolymers. Desirable- * , no polyfunctional cross- linkable monomer is inter ioπaliv added to the solv-er-
ization process, thereby achieving a substantially uncrosslinked alkyl acrylate core polymer rubber, however up to about 0.05 percent crosslinker can be added without significantly affecting the desired low gloss property of the present invention. Suitably, the core polymer has a particle size from 0.05 to 0.8 microns.
Once the core polymer is prepared, the graft- 0 able overpolymer layer is added by polymerization of an additional quantity of an alkyl acrylate monomer and a crosslinking or graftlinking comonomer. Suitable amounts of crosslinking or graftlinking comonomers are from 0.1 to 10 percent by weight. 5
Suitable crosslinking monomers are polyfunc- tional monomers that are well known in the prior art.
Particularly preferred polyfunctional monomers are graftlinking divinyl-substituted monomers, wherein one 0 or more of the vinyl groups is an allyl group or where one group is more reactive than the other under the polymerization conditions employed and a small portion of unreacted vinyl functionality remains after c polymerization of the overpolymer layer as an aid to .attaining graftlinking efficiency. Examples of suitable crosslinking monomers include divinylbεnzene, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, mono-, di-, or polyαlkylene- or 0 polycycloalkyleπe glycol acrylates and methacrylates, butylεne glycol diacrylate, butylene glycol dimethacrylatε, etc.
Examples of suitable graftlinking monomers include allylacryia.e, allylmethacrylate,
diallylmalεatε, diallylphthalate, triallyl isocyanurate, di-, or triallyl cyanuratε.
While the alkyl acrylate rubber has been
_. described as containing a core and a graftable _> overpolymer layer, due to the misclbllity of the substantially uncrossllnked alkyl acrylate polymers and the overpolymer, the resulting composition does not necessarily comprise separatε idεntifiable phases as 10 would be observablε in a traditional "shεll-core" morphology.
A final component of the grafted alkyl acrylate rubber Is the grafted hard phasε. Thε grafting
15 rεaction is accomplished under well known graft promoting processing conditions. Preferably, the desired grafting polymer is polymerized in an emulsion process in the prεsence of the prεviously prepared alkyl acrylate rubber. Suitable grafting conditions
20 are employed to achieve at least some grafting of the hard phase to the alkyl acrylate rubbεr. Grafting levels measurεd as a ratio of wεight of graft tp weight of elastomer phase on the order of 0.01 to about 1.0 t - are desirable.
The above described components (a) and (b) may be separatεly prεparεd in the above described manner and later combined by melt blending, latex blending, or
-, Q othεr suitablε tεchniquεs. Alternativel , at least some of component (a) may be preparεd as a result of thε grafting polymerization process. As is known to the skilled artisan, quantities of ungraftεd matrix polymer are normally prepared in a grafting process.
35 Howεvεr, additional quantities of sεparatεly prepared hard matrix colvmer which r.av be the same or a
different composition than thε graftεd polymεr may bε blendεd with thε resulting composition.
Additional components, well known to be suitably employεd in combination with thermoplastic resins, may bε addεd to thε prεsent invented composition. Examples include antioxidants, colorants, pigments, plasticizers, flow aids, fire retardants, fillers, fibers, and structural reinforcing aids. In addition, other well known impact modifying elastomers may be added to the invented composition in order to provide uniquely tailored resultant propertiεs (as in Examples 1A and 1B below). For example, the prεsεntly invεntεd thεrmoplastic rεsins may bε combined with additional weathεrable impact modifiers, such as EP or EPDM rubbers as well as resins or resin blεnds containing such additional grafted elastomers. Also, conventional crosslinked and graftεd acrylatε εlastomεrs or rεsin blεnds containing such elastomers may be added. The resulting impact and weathεr rεsistant thermoplastic according to the invention may be blended with additional thεrmoplastic matrix polymεrs such as vinyl chloridε homopolymers and copolymers, polyphenylεnε oxidεs, polycarbonates, polyesters, aromatic polyester carbonates, and nylons.
The alkyl acrylate rubber may also be agglomerated into larger size particles utilizing previously known agglomeration technology before grafting if desirεd. Shεar or acidification agglomeration techniques and the use of agglomerating agents including electrolytic and polymeric agglomerating agents such as those disclosed in U.S. Patent 4,419,495 are suitable.
The resins of the invention may bε molded using injection molding or other suitable thermoplastic molding techniques. The resulting molded objects typically possess a low gloss surface. Although the surface gloss may be somεwhat dεpεndent on thε molding temperaturεs and typε and dεsign of thε mold, the 60 degrεe Gardner gloss of- objects molded with the resins herεin disclosed is consistently lεss than about 50 percent and often less than about 30 percent.
Having describεd the invention, the following Examples, Comparative Examples, and Proposed Examplεs are provided as further illustrative and arε not to bε construed' as limiting. Unless indicated otherwisε, parts, pεrcentages and ratios arε mεasurεd by wεight.
PrεDaration A: Uncrosslinked Core Rubber
In a one gallon glass pipe reactor was placed 1030 g water, 2.70 g of NaHCθ3, 1.80 g Na2S 2 θ8, 1.50 g acetic acid, and 13-8 g of a 1000A butylacrylate seed latex (33 pεrcent active). The contents werε purgεd of oxygεn and hεatεd to 65°C whilε agitating at 150 RPM.
Whεn thε tεmpεraturε rεachεd 65°C, a monomεr conadd feed was started consisting of 900 g of n-butylacrylate added at a rate of 180 g/hr for 5 hours. An aqueous feεd was added simultaneously at a rate of 135 g/hr for 5.25 hours and consisted of 0.932 percεnt sodium do εcylbεnzεnε sulfonate soap (NDBS) in -water. The latex was heatεd for 2.0 hours after the monomers had beεn addεd and then stabilized with 7.5 g of a 3/1 mixture of dilaurvthiodiprooinate/tooaπol C 3 antioxiαant mixture. The resulting latex had
particle size of 0.44μ and was about 50 pεrcent soluble (i.e., had a gεl contεnt of about 50 pεrcent) in tetrahydrofuran.
Preparation B: High Crosslink Dεnsity Ovεrpolymεr Shell
Into a glass pipe reactor was placed 2436 g- (810 g of rubber solids) of the core rubber latex of preparation A. An additional 100 g H2O was added to rinse the lines into the reactor. Thε rεactor contεnts wεrε purgεd of oxygεn and hεatεd to 65°C whilε agitating at 150 RPM. A mono εr fεεd consisting of 92.6 g of n-butylacrylate ar.d allylmεthacrylatε (95/5) was addεd
10 ovεr a 1 hour pεriod while an aqueous fεεd consisting of 119.8 g of water (99.0 pεrcεnt), NDBS (0.74 pεrcεnt), and a2S2θ8 (0.26 pεrcεnt) was addεd ovεr a 2 hour pεriod.
15 Thε latεx was heatεd for an additional onε hour aftεr the aqueous feεd had finishεd. Thε particlε sizε o of thε rεsulting rubbεr was 4541A. Thε gel content was 51 percent, and the swelling Index was 31.2 in methyl ethyl ketonε (MEK), whεn tεsted in accordancε with well
20 known test procedurεs such as thosε εssεntially corresponding to those given in aforementioned U.S. Patent 3,830,878, at column 6, lines 17 to 31.
H2O, 1.20 pεrcent NDBS, and 0.36 percent Na S2θ8. The latex was heated for an additional 0.50 hour, steam stripped and stabilized with antioxiαants. The resulting grafted alkyl acrylate rubber concentratε was isolatεd by frεεze coagulation and air dried. The product contained 50.8 percent rubber and had a gel content of 51.4 percεnt.in MEK. Bεcausε of thε significant solubility of the rubbεr, thε ratio of graft to rubbεr (G/R) could not be measurεd, but was εstimated to be betwεεn 0.01 and 0.97.
Blεnds of thε SAN graftεd low crosslink dεnsity alkyl acrylatε rubbεr of prεparation C and various thεrmoplastic rεsins wεre prepared by compounding the rubber concentrate (RC) with other resins on a 0.8 inch Welding Engineers extruder. Samples were preparεd by injεction molding on a 2 oz. Nεgri Bossi injεction molding machinε (barrεl temp 425/450°F, mold temp = 110°F). The 60° Gardner gloss was measured and is reported in Table I for Examples 1A and 1B.
Ex. No Resin Blend Ty 1 E 2 Impact 3 Gloss
IA Rσvel ® 401 5200 67 10.3 26
SAN 1(5.I.) 6
IB BA (27.9%) 5 4590 90 6.9 21
RC (29.5%) ^
SAN (42.6%) δ
1 Tensilε Yield (lb/in2) ASTM 638 at 0.2 inches/minute
2. Elongation at Rupturε ( % ) ASTM 638 at 0.2 inches/minute
3 Notched Izod (ft-lbs/in notch) ASTM D-256
4 An EPDM rubber-modified SAN resin available from Thε Dow Chεmical Company
A polybutylacrylate rubber-modified SAN resin. The acrylate rubber is a conventional homogenεous, crosslinkεd, rubbεr particle of volume average particle size, 0.15μ, and contains 0 Λ0% crosslinker and .0% graftlinker. The rubber particles are grafted with SAN. Rubbεr content is 53.8^.
Tyril ® 111 brand styrenε acrylonitrile copolymer available from The Dow Chεmical Company.
It is sεεn that thε rεsln blεnds of thε invention possess good impact resistance and are well suitεd for thε prεparation of vary low gloss moldεd objεcts.
Co Darativε Trials
The following Comparative Examples are not actual prior art. However, they help understanding of the surprising technical advance of thε invention.
Comparative Example 2A
This Comparative Examplε was εssεntially similar to Examplε 1A εxcεpt that all thε SAN-graftεd c rubbεr components werε prεparεd with crosslinked cores The product had a high gloss of 82 (rather than 26 as in Example 1A) .
In particular, the "RC" component was prepared
10 in a manner similar to Preparations A and B in Example 1, except for using polyvinyl crosslinkers in thε core (about 0.25 percent) to get a rubbεr having 96.5 percεnt gεl content and a swelling index of 6.3 in MEK. This rubbεr was then grafted with SAN as in Preparation 15 C in Example 1.
The resin was then blendεd, molded, and testεd εssentially as in Example 1, and the following results werε obtainεd: Ty, 5720; E, 11; impact, 3-8; and gloss, 0 82.
Comparative Examplε 2B
This Comparative Example was essentially 5 similar to Example 1B except that all the SAN-grafted rubbεr componεnts wεre rεplaced by an equal amount of polybutylacrylate rubber-modified SAN resin. The product had a gloss of 62 (rather than a gloss of 21 as in Example 1B) . 0
In particular, a polybutylacrylate rubber- modified SAN resin v.as preparεd as in Comparativε 2A. Thε rubber had 92.7 percent gel and swelling index of 8.4. 5
The resin was thεn blendεd, moldεd, and tεstεd essentially as in Examplε 1 , and the following rεsults were obtainεd: Ty, 5340; E, 30; impact, 2.9; gloss, 62.
Proposed Examples 3A and 3B
From thε rεsults obtainεd in Examples 1 and 2, it is proposed that even lower gloss values might be obtained by using a completε absεnce of crosslinking in any of the acrylatε rubbεr corε. Thus, it is proposεd that Examples 1A and 1B be repεated except that thε usε of crosslinking agεnt be omitted in preparing the polybutylacrylate rubber corε.
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