JPH03122168A - Blow molding method and blow molded article - Google Patents

Abstract

PURPOSE: To obtain a hollow article having a uniform wall thickness and excellent in shock resistant strength, luster, and transparency by blow molding a resin composition containing a thermoplastic resin and a specified graft copolymer.

CONSTITUTION: A thermoplastic resin composition containing (A) a thermoplastic resin (those which have not been used in blow molding are allowed) and (B) a graft copolymer in an amount of 0.1 to 10% (based on the total weight of the composition) containing B₁: polyolefin backbone and B₂: a methacrylic chain polymer made up of 80 wt.% methacrylic ester monomer of the formula wherein R represents an optionally substituted alkyl, aryl, or alkaryl and less than 20 wt.% styrene type monomer or acrylic monomer capable of copolymerization therewith, and having a weight average molecular weight of 20,000 or more with it covalently bonded to B₁ in a weight ratio of (1:9) to (4:1) is blow molded to obtain a hollow article, such as a duct and a bumper of automobiles.

COPYRIGHT: (C)1991,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of blow molding a thermoplastic resin composition to make hollow articles, and to products so made.

BACKGROUND OF THE INVENTION Blow molding is used to make hollow articles such as bottles and containers. There are two types of blow molding methods: extrusion blow molding (including accumulator molding, especially for the molding of large products) and injection blow molding (including stretch blow molding). Parisons in the form of tubes with or without bottoms are formed by extrusion or injection and then blown to size.

It is desired that the soft parison has high melt strength. Otherwise, the parison will sag too much before being blown. This is called drawdown. High melt strength also makes blow molded parts more uniform in thickness,
This is important because even the thinnest parts of the molded part must meet specifications. Because of the drawdown, blow forming of large articles is not easy where a large parison must first be made. Also, some resins and resin compositions cannot be blow molded due to their low melt strength.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a blow-molding method and a product made thereby, which solves the above-mentioned problems.

The present invention provides a method for making a hollow article by blow molding a thermoplastic resin composition, wherein the thermoplastic resin composition is covalently bonded to (a) a thermoplastic base resin and (b) a polyolefin backbone and a backbone. Approximately 0 graft copolymers with methacrylate chain polymers
, 1 to about 10% by weight (based on the total weight of the resin composition), and the methacrylate chain polymer has at least about 80% by weight of the formula CH2=C(CH3)COOR, where R is alkyl, aryl, substituted alkyl. , substituted aryl, alkaryl, or substituted alkaryl) and less than about 20% by weight of an acrylic or styrenic monomer copolymerizable with the methacrylic ester; The method is characterized in that the methacrylate chain polymer has a weight average molecular weight greater than about 20,000 and is present in a weight ratio of about 1:1 to the backbone.

Ru.

The graft copolymers used in the present invention are described in applicant's Japanese Patent Application No. 1-80238 and have a weight average molecular weight greater than about 20,000 on a nonpolar polyolefin backbone in solution. , and present in a weight ratio of about 1:9 to 4:1 to the polyolefin. The graft copolymer has at least about 80% by weight of the formula CH2=C
(CH3)COOR (where R is alkyl, aryl,
a methacrylic ester monomer (which is a substituted alkyl, substituted aryl, alkaryl or substituted alkaryl) and less than about 20% by weight, based on the total weight of the monomers, of an acrylic or styrenic monomer copolymerizable with the methacrylic ester; guided by the body.

This results in a constant low radical concentration, i.e. the radical “
This is accomplished by adding methacrylate monomer to a polyolefin solution with an initiator that generates a "flux" at solution temperature. These radicals initiate polymerization of the monomer and form a covalent bond with the stem.

The resulting copolymer material (hereinafter referred to as "concentrate") is
As a result of the method in which the material is made, or after it is made, it may be mixed with a thermoplastic resin, such as a polyolefin. Then, it can be extruded directly or after pelletization into a desired shape. In both cases, the resulting mixture contains similar ungrafted polymers,
That is, compared to polyolefins without high molecular weight chains or covalently bonded chains, they exhibit relatively high tensile modulus and high sag resistance without increased melt viscosity.

A method for making copolymers having relatively large weight average molecular weight (MW) polymer chains involves dissolving or swelling a polyolefin in an inert hydrocarbon solvent to obtain a polymer chain of at least about 140 MW.
℃ to dissolve the polyolefin. While stirring the solution, monomers are introduced along with an initiator that generates a constant low radical flux at the temperature of the solution. The radicals initiate polymerization of monomers and the formation of covalent bonds on the polyolefin backbone. The reaction mixture is
It can be solidified by removing the solvent. the obtained substance,
The concentrate thus consists of chain-grafted polyolefins, unreacted polymers, ie chain-free polyolefins, and ungrafted methacrylic ester polymers. It can be pelletized, mixed with another thermoplastic, such as a polyolefin, and extruded into the desired shape. Alternatively, the reaction mixture may be directly extruded in a devolatilization extruder to evaporate the solvent and residual monomer, and then mixed with a polyolefin or the like and extruded to form a product in the form of a sheet or the like.

In the following, LDPE has a density of about 0.91 to 0.94
g/cc normally branched low density polyethylene; HDPE
is high-density polyethylene with a density of about 0.95 g/CC or more, LLPDE is linear low-density polyethylene with a density of about 0.91 to 0.95 g/CC, and EPDM is a polyethylene containing ethylene, propylene, and 1,4- Includes rubbery terpolymers of non-conjugated diene monomers such as xadiene or ethylidene norbornene.

Graft copolymers that can be used include polyolefin:acrylic polymers or copolymers in a ratio of 10:9.
0-80:20, preferably 20:80-80
: 20 things can be mentioned.

Although the molecular weight of the polyolefin polymers that form the backbone of the graft copolymer should be large enough to provide a large amount of nonpolar polymer when grafted, most graft copolymers It should be small enough to have one acrylic polymer chain grafted onto the chain. Approximately 200,000~800,
Polyolefin backbones having a molecular weight of about 50,000 Mw are particularly preferred, although polyolefins having a molecular weight of about 50,000 to 200,000 can be used for certain beneficial effects.

It is known that melt flow rate (mfr) correlates well with weight average molecular weight. mf for the polyolefin backbone used to prepare the graft copolymers of the present invention
The preferred range of r values is according to ASTM standard method D-1238.
It is about 20 to about 0.6 g/10 minutes as measured at .

A preferred monomer is methyl methacrylate.

This or other C2-4 alkyl methacrylate alone may be used. Up to 20% of methacrylates of higher alkyls such as dodecyl, aryls such as phenol, alkaryls such as benzyl and/or cycloalkyls such as cyclohexyl can be used.

Furthermore, up to 20% (preferably less than 10%) of the following monomers can be incorporated with the methacrylate ester forming the majority of the monomers: methacrylic acid, methacrylamide, hydroxyethyl methacrylate, hydroxyethyl methacrylate, Alkoxyalkyl methacrylates such as ethoxyethyl methacrylate, alkylthioalkyl methacrylates such as ethylthioethyl methacrylate, methacrylamide, t-butylaminoethyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminopromethacrylamide, glycidyl methacrylate, methacryloxypropyl triethoxy Silane, acrylate monomer (ethyl acrylate, butyl acrylate and congeners), styrene, acrylonitrile, acrylamide, acrylic acid,
Acryloxypropionic acid, vinylpyridine and N-vinylpyrrolidone. Additionally, up to 5% maleic anhydride or itaconic acid may be used. In order to efficiently produce homogeneous non-gelled graft polymers in good yields,
It is important that chain migration of the polymeric chains into their own polymer is minimal compared to migration with the polyolefin chains.

The molecular weight of the acrylic graft, as measured by the weight average molecular weight of the ungrafted acrylic polymer with which it is made, is about 20,000 to 200,000, with a preferred range of 30,000 to 150,000.

The process of graft polymerizing monomers results in the production of ungrafted and grafted materials. The amount of grafted material ranges from 5% to 50% of the total acrylic polymer or copolymer produced. Graft copolymers are prepared by polymerizing monomers in the presence of nonpolar polyolefins. The method is carried out in a solvent that swells or dissolves the non-polar polymer. The solvent may also have no or low chain transfer ability, such as branched or unbranched aliphatic hydrocarbons, chlorobenzene, benzene, t-butylbenzene, anisole, cyclohexane, naphtha, and dibutyl ether. Can be mentioned. Preferably, the solvent is easily removed by extrusion evaporation, so the boiling point is below 200°C, preferably about 1
The temperature is below 50°C.

Also, boiling points above about 100° C. are preferred to avoid excessive pressure.

The final solids content (including polyolefins and acrylic polymers) depends on the viscosity and how well mixed. Practical limits are between 20% and 70%, but with good mixing it is economical to achieve higher solids contents. The preferred range of solids content is from about 35% to about 60%.
%.

It is preferable to add the monomer gradually or in multiple steps. If desired, the monomer feed may not be the same throughout; the monomer can be concentrated in one portion of the polymer, for example by including the entire amount of monomer used in small amounts in the last 0-20%. You can also do it.

The temperature during polymerization ranges from 110 to 200'C, with a preferred range of 130 to 175'C. Particularly preferably, the temperature is 145 to 160°C. The pressure can be from atmospheric to superatmospheric, or as high as 210 OkPa, or any pressure necessary to maintain the reaction mixture in the liquid phase at the polymerization temperature.

Unreacted monomer concentration should be kept low during the reaction. This adjustment is done by balancing the radical flux and monomer feed conditions.

In the polymerization, oil-soluble thermal free radical initiators are used. The initiator operative in the process of the invention is about 60 to about 2
It has a half-life of 1 hour at 00°C and preferably has a half-life of 1 hour in the range of 90-170°C.

The initiator is introduced with the monomer during the polymerization so as to maintain the radical flux approximately constant during most of the polymerization. By doing so, a suitable high molecular weight, high grafting efficiency and desired molecular weight distribution can be achieved and no gels will form.

Radical flux is defined as the calculated rate of free radical production and can be expressed in number of radical equivalents/N/min. Although it cannot be measured experimentally, it can be calculated from the known rate of decomposition of the free radical initiator present at any given time and its instantaneous concentration. The decomposition rate of the initiator is determined from the literature and the concentration is a known constant when the initiator is fed continuously or (in the case of a single feed of the initiator) from the known decomposition rate constant and the feed. It can be calculated from the elapsed time.

The radical flux is maintained uniformly, and the calculated value of the radical flux is 0.00001 to 0.0005 equivalent radial force/1/
Good results are obtained when the range is within minutes. Preferably 0.00002 to 0.0002 equivalent radial force/f
J/min range. Radical flux depends on the particular initiator used, its concentration and rate of decomposition, and the selected reaction temperature. The decomposition rate is determined by rThe polymer
Handbook (Polymer Handbook)” Volume 2
Edition, BrandrtJp and Immer (LL
It edition.

Wiley and 5ons, New York
(1975) can be found in data tables such as
Alternatively, given by the manufacturer. Even if the exact rate constant at the temperature in question is not known, the activation energy is often given and the rate can be calculated from it. Radical flux is calculated by the following equation.

Radical flux = 2 (kd) (60) (I >
(where kd is the decomposition rate constant (sec-1) of the specific initiator
, and ■ is the concentration of the initiator (mol/fl).

) In a batch reaction, ■ is the initial feed ■.

The radical flux is not constant because it always decreases from . If the initiator is fed continuously, calculations must be made to determine the instantaneous concentration of the initiator, but especially if the initiator feed is carefully regulated, the value of this concentration can be reduced for batch reactions. is much more constant than

This step can be carried out in a semi-continuous or continuous manner. Monomers, solvents and initiators may be added in a similar manner as described above. The polymer may be separately dissolved in a solvent and added at a rate substantially equivalent to the rate of product removal, or the polymer may be melted and subjected to the reaction as a solid via an extruder.

A holding time can be provided after polymerization. The mixture is then stripped to remove solvent and unreacted monomer. Acceptable devolatilization devices include devolatilization extruders, rotating membrane evaporators, or other convenient stripping devices known in the art. The polymerization reaction mixture can be conveyed batchwise or continuously to the evaporation device.

Suitable additives desirably present in the isolated graft copolymer are mixed into the graft copolymer solution/suspension before, during or after the volatilization step. If such additives do not affect the grafting reaction, they may be added before, during or after the polymerization step. Such additives may also be added when the graft copolymer is mixed with the matrix polymer. Such additives include benzotriazoles, sterically hindered amines,
Light or heat stabilizers such as alkyl polysulfides such as dialkyl disulfides; lubricants or plasticizers; flame retardants and the like. Preferably, a disulfide such as di-n-dodecyl sulfide or di-t-dodecyl disulfide is added at a level of about 0.05% by weight based on the total weight of the graft copolymer and matrix polymer. , the acrylic part of the graft copolymer,
Preferably, the matrix is stabilized against thermal degradation during additive mixing or melt processing during compounding and extrusion.

The second class of stabilizers are tris(polyalkylhydroxybenzyl)-s-triazinetriones. Tris-(4-t-butyl 3-hydroxy-2,6-
dimethylbenzyl)s-)-riazine-(IH, 3H,
5H)-trione is preferred.

Stabilization can also be achieved by including an alkylthioalkyl (meth)acrylate, preferably ethylthioethyl methacrylate, in the acrylic monomer during graft polymerization.
It can be applied to the acrylic portion of the graft copolymer. The product is then isolated by stringing, cooling, cutting, drying and bagging or other known collection methods.

The thermoplastic base resin (matrix resin) (a) may be one that could not be conventionally used in blow molding or one that has been used. Examples of such thermoplastic base resins include polyolefins such as polypropylene, polyethylene (such as HDPE, LDPE and LLDPE), polybutylene, ethylene-propylene copolymers of any ethylene to propylene ratio, any ethylene to propylene ratio and up to 10%. EPDM terpolymers of diene monomers, poly(1-butene), polymethylpentene, ethylene-vinyl acetate copolymers with vinyl acetate content up to 25%, ethylene-methyl acrylate copolymers, ethylene-methyl methacrylate copolymers, and ethylene-ethyl acrylate copolymers. Other thermoplastic resins include polyamide, polycarbonate, polyester (PET, PBT, etc.), pvc, AB
S, EOOH, polyacrylic resins and imidized resins thereof, polyphenylene oxide, polysulfone, and the like. Mixtures of the above resins may also be used.

Optionally, the composition comprising the graft copolymer or concentrate and the thermoplastic base resin may further contain organic or inorganic fillers such as carbon black, talc, calcium carbonate, mica, fibers such as glass fibers, antistatic agents,
Impact modifiers, colorants such as pigments or dyes, stabilizers against heat, light or ozone etc., flame retardants such as halogen- or phosphorus-containing compounds and/or blowing agents may be included.

The amount of graft copolymer is approximately 0.06% based on the total resin composition.
1 to about 10% by weight, preferably about 0.5 to about 5% by weight. If the amount exceeds the upper limit, it is economically disadvantageous. If the amount is less than the lower limit, the intended effect cannot be sufficiently obtained.

The thermoplastic resin composition is first extruded or injected into a parison at high shear rates. The formed parison is allowed to sag more or less at a low shear rate before being blown. The graft copolymers used in this invention significantly increase melt strength at low shear rates. Accordingly, the parison sag is much less, which makes the blowing process easier to operate and also makes the thickness of the formed article more uniform. Less sag allows larger and/or thicker articles to be formed by blow molding. Articles requiring greater strength can now be made by blow molding. It also allows for larger blow ratios.

Surprisingly, the graft copolymers used in the present invention do not significantly increase melt strength at high shear rates. Therefore, when the parison is extruded or injected, the viscosity of the molten resin composition according to the invention is not undesirably high. Otherwise extrusion or injection becomes difficult. Graft copolymers also provide faster melt times and lower peak torques, both of which result in faster extrusion or injection operations.

Products made according to the invention have a more uniform thickness than those blown without the graft copolymer.

It has higher stiffness (flexural elasticity), higher impact strength and higher gloss. These allow the walls of the product to be designed thinner. Depending on the case,
Higher transparency is obtained, which is important for many packaging applications.

Examples of articles blow molded according to the invention include ducts, automobile bumpers, fuel tanks, other automobile parts, hollow parts of office equipment, packaging articles, hollow containers such as bottles with especially barrier properties, coolant overflow containers and aircraft Transport machine parts such as steam recovery bins are mentioned.

The invention is further illustrated by, but not limited to, the following examples.

Example 1 A polypropylene-acrylic graft copolymer was prepared with 5% ethyl acrylate (EA) in the presence of polypropylene.
It was made by polymerizing a 95% methyl methacrylate (MMA>monomer mixture (polypropylene:monomer weight ratio = 0.67:1).

Di-t-butyl peroxide (DTBPO) 0,0
Radicals were generated at a rate (radical flux) of 0.0010 mol/1/min. Monomer and initiator were fed over a period of 60 minutes and the theoretical amount of solid obtained at the end of the reaction (100%
conversion rate) is 55%.

6,6 equipped with double helical stirrer (it5rpm>
A 1-volume reactor was charged with 1780 g of a 2-methylalkane inert hydrocarbon solvent mixture having 6 to 12 carbon atoms and polypropylene (mfr=4) at 880 K and heated to 175°C. After 2 hours the temperature was lowered to 155°C and the batch was stirred for an additional hour. The two solutions were added over a 2 minute period. The first solution was 1.04 g di-t-butyl peroxide dissolved in 21 g hydrocarbon solvent, and the second solution was 2.1 g ethyl acrylate and 42.
0.06 g of di-t-butyl peroxide was dissolved in methyl methacrylate. During the next 58 minutes, 1.87 g di-t-butyl peroxide and 62 g
Methyl methacrylate of ethyl acrylate 1215
The solution in g was fed at the same feed rate as the second feed. This feeding schedule ensures o, oooi during the feeding time.
A radical flux of o was obtained. After the feeds were complete, the reaction was held at 155° C. for an additional 15 minutes. Then 200-250
30 mm Werner-Pfleidere with two vacuum vents at
r) Volatilization by passing through an extruder. The resulting concentrated product (concentrate) had a composition of 56% (by elemental analysis).
It is a mixture of meth)acrylates. From the extraction results, 15.9% of the polymerized (meth)acrylic monomer was grafted, and the Mw of the (meth)acrylic polymer was 91.3.
It turned out to be 00. This concentrate can be mixed with other thermoplastic polymers such as polypropylene.

The following table shows the effect of mixing various levels of the above concentrates on improving the sag resistance of polypropylene homopolymer having a melt flow rate (mfr) of 4.

In the above, the sagging test is performed using 10x 10x O,
The test was performed on No. 151 compression molded sheets. This sheet was held in a frame having a 7.61 square opening.

To measure sag, we attached metal gauges to the front and back of the frame. The frame and sheet were placed in a hot forced air oven (typically 190'C). The amount of sag in the center of the sheet was then recorded as a function of time. Initial sag was typically recorded at 2.5 cm, but for slow sagging materials, 16WI
n and a small droop was recorded. Data recording is
until 10.2am or 30 minutes, whichever occurred first.

"Slope" represents the slope when plotted as the natural logarithm of sag (am) versus time, resulting in a straight line. A large slope indicates that the material is sagging rapidly;
A small slope indicates slow sagging. Comparing slopes in this manner has the advantage of eliminating differences in oven cooling when the sample is introduced (due to differences in oven open time, room temperature, etc.).

Examples 2-5 This example demonstrates making graft copolymers in bulk and making bottles by blow molding.

Several preparations were put together. In all but the last of these preparations, radicals are generated at a rate (radical flux) of 0.000070 mol/I/min. The monomer and initiator are fed over 120 minutes and the theoretical (100% conversion) solids content at the end of the reaction is 50%.

380.1 with pitched blade turbine agitator! 86. into the reactor. hg of hydrocarbon solvent and 34.5 kg of polypropylene homopolymer (mfr=4>.3
After removing oxygen in a cycle (vacuum to remove gas, then pressurize to atmospheric pressure with nitrogen), pressurize to 103 kPa with nitrogen and heat to 150° C. for 2 hours. 150 batches
A pressure of 241 kPa was maintained while holding at °C for 3 hours. The two solutions were added over 15 minutes.

The first solution was 59g DT in 841g hydrocarbon solvent.
Consists of BPO. The second solution consists of 0.32 kg ethyl acrylate and 6.14 kg methyl methacrylate. Then continuing the addition of the first solution at a lower rate,
An additional 103 g of DTBPO and 147 g over 105 minutes
9g of hydrocarbon solvent was fed.

At the same time, 2.26 kg of ethyl acrylate and 43.0
The monotonic addition of kg methyl methacrylate was continued over a period of 105 minutes. The reaction exotherm raised the temperature to about 160°C.

After the feed was completed, 5 kg of hydrocarbon solvent was fed to the reaction mixture.

The reaction mixture was held in the reaction vessel for an additional 30 minutes.

It was then transferred to a second reactor, also under pressure at 150°C. During the transfer, 320. 8 in a hydrocarbon solvent of
0 g of di-t-dodecyl disulfide solution was added to the second reactor. Also during this transfer, 4.53 kg of hydrocarbon solvent was fed into the reactor three times. The material in this second reactor was transferred to a 20.3 mm Welding Engineers (We
The mixture was fed into a twin-screw extruder, where it was removed by volatilization.

During stripping off, the next batch was prepared in the reactor. It was transferred to the extruder feeder while extrusion continued. In this manner, several batches were made in a "semi-batch" manner, ie batchwise in the reactor with continuous feed to the extruder.

In the final preparation of the formulation, the radical flux was 0.0
00050 (42 g DTBPO + 858 g of hydrocarbon solvent in the first feed, 73 g DTBPO + 1502 g of hydrocarbon solvent in the second feed).

The finished blended graft copolymer was made by blending pellets from 13 batches made as described above and one batch of the last variant. All samples from the individual batches gave acceptable sag resistance when tested on polypropylene.

The matrix polymers of Examples 2 and 3 were blended in varying amounts up to 5% by weight with one of the two commercially available polypropylenes used for bottle blow molding. Propylene random copolymer (mfr) believed to contain ~4% ethylene
= 2 > , Trademark Eina7231 (Fina O
IL and Chemica 1, Dallas, Texas). The matrix polymer of Examples 4 and 5 was a propylene homopolymer (mfr=2), trademark N
orchem 7200GF (Quantum Che
mica, Inc., Division 131, Rolling Meadows, Illinois). The resins were tumble mixed to form a formulation.

The sample was transferred to a Jomar machine model 40 (J).
Omar, Pleasantville, New Chassis)
injection blow molded. The molten resin formulation was injected into a four-cavity mold (two cavities were blocked) on a core bin with air holes in the bottom to form an inflatable parison.

The mold was heated and designed to create a pattern on the tip that would allow a cap to be attached after molding.

The temperature of the mold was controlled at the neck, walls and bottom of the bottle.

The parison was transferred to a second location where it was expanded into a bottle mold, then transferred to a third location where it was cooled and removed.

The 103.5 ml Koshyobin bottles were evaluated for surface gloss, transparency, thickness uniformity, wall strength, etc., as well as ease of molding, in comparison to unmodified controls.

First day and retreat 2 Fina7231 --- 243 7
7.7 10448.93 Fina7231
5% 249 82.211048°94 N
OrChem---24377,710448
,95Norchem 5% 249 82
．． 2 110 48.9 Comparing the bottle of Example 3 to the control of Example 2, there is a small improvement in gloss, a noticeable increase in adhesion transparency, and an increase in hardness (st i Hness
) showed significant improvement. A similar advantage over the control was observed using 1% grafted polymer in the matrix resin of Example 2. The transparency effect is as shown in Example 5.
It was not observed in the bottle of Example 4 compared to the control example 4.

Example 6 The graft copolymer made in Example 2 was blended with various polyethylenes and subjected to a sag test.

The results were as follows.

LLDPE (Dowlex 2517) LLDPE (D
owlex 2047) LLDPE (Nipolon
L F15-R)25 (21,2) 2.19
1.862.3 (1,99) 0.30
0.110.8 0.17 HD without drooping
PE (Dow25055N) 25 (2
4,0) 2.6B 2.19HDPE(Do
w 04052Nl 4.0 (4,21)
0.58 0.25 Among the melt index values, the numbers in front of parentheses are literature values, and the values in parentheses are values measured according to ASTM Condition E on extruded pellets.

It is clear that the addition of 5% graft copolymer greatly reduced sag. Similar to the previous examples, polyethylene can also be modified with graft copolymers according to the invention.

Claims (1)

[Claims] 1. A method for producing a hollow article by blow molding a thermoplastic resin composition, wherein the thermoplastic resin composition comprises (a) a thermoplastic base resin, (b) a polyolefin trunk, and About 0 graft copolymers with covalently bonded methacrylate chain polymers
．． 1 to about 10% by weight (based on the total weight of the resin composition), and the methacrylate chain polymer has at least about 80% by weight of the formula CH_2=C(CH_3)COOR, where R is alkyl, aryl, substituted alkyl, substituted aryl, alkaryl or substituted alkaryl) and less than about 20% by weight of an acrylic or styrenic monomer copolymerizable with the methacrylic ester; A method according to claim 1, wherein the methacrylate chain polymer has a weight average molecular weight greater than about 20,000 and is present in a weight ratio of about 1:9 to about 4:1 to the backbone. 2. The hollow article according to claim 1, wherein the hollow article is a duct, an automobile bumper, a fuel tank, a hollow part of office equipment, a packaged article, a hollow container, or a transport aircraft part such as a coolant overflow container and a vapor recovery bin in an aircraft. Method.