CA1096536A - Polymers for extrusion applications - Google Patents
Polymers for extrusion applicationsInfo
- Publication number
- CA1096536A CA1096536A CA271,939A CA271939A CA1096536A CA 1096536 A CA1096536 A CA 1096536A CA 271939 A CA271939 A CA 271939A CA 1096536 A CA1096536 A CA 1096536A
- Authority
- CA
- Canada
- Prior art keywords
- epoxy
- branching agent
- isocyanate
- branched chain
- melt strength
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/40—High-molecular-weight compounds
- C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
- C08G18/4205—Polycondensates having carboxylic or carbonic ester groups in the main chain containing cyclic groups
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/40—High-molecular-weight compounds
- C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
- C08G18/4205—Polycondensates having carboxylic or carbonic ester groups in the main chain containing cyclic groups
- C08G18/4208—Polycondensates having carboxylic or carbonic ester groups in the main chain containing cyclic groups containing aromatic groups
- C08G18/4211—Polycondensates having carboxylic or carbonic ester groups in the main chain containing cyclic groups containing aromatic groups derived from aromatic dicarboxylic acids and dialcohols
- C08G18/4213—Polycondensates having carboxylic or carbonic ester groups in the main chain containing cyclic groups containing aromatic groups derived from aromatic dicarboxylic acids and dialcohols from terephthalic acid and dialcohols
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/40—High-molecular-weight compounds
- C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
- C08G18/4263—Polycondensates having carboxylic or carbonic ester groups in the main chain containing carboxylic acid groups
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
- C08L67/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
Abstract
Abstract of the Disclosure The present invention provides a process for preparing branched chain, thermoplastic polymers having improved melt strength and die swell properties. This process comprises reacting at least one thermoplastic polymer capable of reaction with an epoxy or isocyanate functionality, the polymer being in the molten state, with at least one branching agent selected from the group consisting of epoxy containing at least two epoxy groups per molecule of epoxy branching agent, and iso-cyanate containing greater than two isocyanate groups per molecule of isocyanate branching agent, to produce branched chain thermoplastic polymers having a melt strength ratio of T2/T2 of less than about 2.0 at 235°C.
The molten, thermoplastic, branched chain polymer reaction product has increased melt strength and intrinsic viscosity.
The increased molt strength polymers also have improved die swell characteristics and are useful in extrusion applications such as blow molding.
The molten, thermoplastic, branched chain polymer reaction product has increased melt strength and intrinsic viscosity.
The increased molt strength polymers also have improved die swell characteristics and are useful in extrusion applications such as blow molding.
Description
6~36 Background o~ the Inven-tion In blow molding processes, molten resin must form into stable parisons for a time long enough to permit a mold to enclose the parison. If these molten resins do not possess suf~icient "melt strength" or melt viscosity, the parisons will tend to elongate or draw under their own weight and either not be blow moldable or result in blow molded articles which have non-uniform wall thicknesses, low surface gloss, poorly defined sample shape, and a large number of pitmarks.
Polymers such as polyesters, polyamides, polyethers, and polyamines when melted generally form thin liquids naving low melt viscosities and poor melt strengths. These low melt viscosity materials are unsuited or are only poorly suited for the manufacture of extruded shapes, tubes, deep drawn articles, and large blow molded articles. In order to overcome this disadvantage and to convert these polymers to a form better suited for the above-mentioned manufacturing techniques it is known to add compounds to the plastics which will increase their melt viscosities.
The materials which are added to increase the melt viscosity of the plastics are generally cross-linking agents, as described, for example, in United States Patent 3,378,532. Such cross-linking agents may be added during the condensation reaction by which the plastics are formed, and/or to the plastics after their formation (prior to, or during their melting). Examples of cross-linking agents which may be added to the plastics after their formation and before or after their melting in order to increase the melt viscosity include compounds containing at least two epoxy or isocyanate groups in the molecule, organic phosphorus compounds, peroxides, bishaloalkylaryl compounds, and polyesters o~ carbonic acid.
~ o~9~53'6 These known_cross linking agents which are added to increase the melt viscosity of the polymer are not completely satisfactory. They may, for instance, cause an excessively rapid and large increase in viscosity or form reaction products which have an adverse influence on the quality of the plastics.
Furthermore, the results obtained with the use of these known cross-linking agents are not always uniform or reproducible.
For example, when polyesters of carbonic acid are used to increase the melt viscosity, the degree of viscosity increase is generally dependent not only upon the amount of additive used but also upon its molecular weight and on the stage of the polycondensation reaction at which the addition takes place.
Besides having sufficient melt viscosity or "melt strength", polymers which are to be used in blow molding and related applications should also possess sufficient die swell, i.e., the molten polymer should expand as it is released from the extrusion die. This die swell is important for blow molding applications since (a) the larger the diame-ter of ; the extruded polymer, the easier it is for air to be blown into the parison, and (b) the greater the die swell the greater the expansion of-the molten polymer to fit the particular mold.
Polyesters having low intrinsic viscosities are particularly difficult to blow mold. The prior art illustrates the use of nurnerous additives to modify various properties of polyesters. For example~ United States Patent 3,376,272 discloses a processforthe preparation of branched chain, high molecular weight thermoplastic polyesters having a multiplicity of linear non-cross.ilinked polyester branched chains from dicarboxylic acid anhydrides, monoepoxides, and an alcohol compound by reacting these compounds at a temperature below 150C. However, 1~9~36 the polyesters described in this patent are formed from s.nhyariaes and are therefore not crystalline. Non-crystalline pol~Jmers tend to take longer time to set up in a mola and thus are not suitea or are only poorly suited for blow molding and related applica-tions.
As indicated above, compounds containing epoxy groups in the molecule have been used to increase the melt viscosity of polyesters (see, for example, United States Patent 2,830,031).
But although the use of epoxies as cross-linking agents for polyesters is known, little appears known about the use of epoxies as reactants which promote the branching (and hence increase the "melt strength") but not the cross-linking of polyesters.
United States Patent 3,547,873 disclosesthe prcduction of thermoplastic molding compositions from linear saturated polyesters and polyfunctional epoxides. This process, however, also yields products which lack the melt strength ana die swell necessary for blow molding applications.
Polyisocyanates have also been used to increase the melt viscosity of polymers such as polyesters. For example, United States Patent 2,333,639 aiscloses the reaction of low intrinsic viscosity, low molecular weight polyesters with polyisocyanates (e.g., a diisocyanate) at temperatures up to 300C to form higher intrinsic viscosity, higher molecular weight, fusible polyesters, but this process results in relatively low melting, linear, soft amorphous polyesters with poor melt viscosity and poor die swell properties.
gL~g~S36 United States Patent 3,304,286 discloses the xeaction of a poly-ester with a polyisocyanate such as diisocyanate. However, this process yields products having straight chain non-branched structures. These products thus lack the melt strength and die swell needed for blow molding applications.
Furthermore, United States Patent 3,692,744 discloses the pre-paration of polyester molding materials which can be injection lded by having present in the polyes~erifica~ion mixture, besides the terephthalic acid and diol con~onents, 0.05 to 3 moles percent, based upon the acid component, of a compound containing at leas$ three ester forming groups such as a polycarboxylic acid, a polyhydric alcohol, or a hydroxy carboxylic acid.
The use of epoxy or isocyanate compounds is not disclosed, however.
The search has continued foT improved processes for preparing polymers having increased melt strength. The present invention has resulted from that search.
It would be advantageous to avoid or substantially alleviate the above problems of the prior art.
In particular~ it would be advantageous to have a process for preparing impToved polymer compositions having improved melt strength and die swell characteristics.
It would be advantageous to have a process for preparing improved polymer compositions useful in blow molding and profile extrusion applications.
It would be advantageous to have the improved polymer compositions prepared by these processes.
It would also be advantageous to have an improved polymer molding pxocess utilizing these new polymers.
In one aspect, the present invention provides a process for pre-paring branched chain thermoplastic polymers having increased melt strength which are useful in ext~usion applications. This process comprises reacting at least one thermoplastic polymer which is in the molten state and which ~L~3~6~36 is capable of reaction with an epoxy or isocyanate functionality, wi~h at least one branching agent selected from the gTOUp consisting of epoxy con-taining at least two epoxy groups per molecule of epoxy branching agent, and isocyanate containing greater than two isocyanate groups per molecule of isocyanate branching agent, to produce branched chain thermoplastic polymers having a melt strength ratio of Tl/T2 of less than about 2.0 at 235 C.
In another aspect~ the pxesent in~ention provides the melt strength improved thernoplastic polymers produced by this process.
In still another aspect, there is provided an improved molding process which comprises ~orming a melt of the above-described melt strength improved thermoplastic polymer into a desi~ed article and cooling the molten polymer.
According to a particular embodiment of the present invention there is provided a process for preparing branched chain thermoplastic polyesters of incTeased melt strength useful in extIusion applications, which pTOCeSS
comprises reacting a~ least one thermoplastic polyester capable of reaction with an epoxy or isocyanate functionality, said polyester being in the molten state, with at least one branching agent selected from the group con-sisting of epoxy containing at least two epoxy groups per lecule of epoxy branching ag~nt and isocyanate containing greater than two isocyanate groups per molecule of isocyanate branching agent to pYo~uce said branched chain ther~oplastic polyesters having a melt strength ratio of Tl/T2 of less than about 1.8 at 235 C.
The present invention also provides a process for preparing branched chain polybutylene terephthalate having increased melt strength and useful in ex~rusion applications which process comprises reacting from about 95 to about 99% by weight polybutylene terephthalate in the molten state, with from about 1 to about 5% by weight of at least one branching agent selected from the group consisting of epoxy containing at least two epoxy groups per molecule of epoxy branching agent, and isocyanate containing ~ 653~
greater than two isocyanate groups per molecule of isocyanate branching a~ent wherein said reaction is carried out at a temperature of from about 220 to about 280C and at substantially atmospheric pressure to produce said branched chain polybutylene terephthalate having a melt strength ratio of Tl/T2 of less than about 1.6 at 235C.
The present invention according -to a further aspect provides a branched chain, improved melt strength thermoplastic polymer suitable fo~
extrusion applications and having a melt strength ratio of Tl/T2 of less than about 2.0 at 235C wherein said branched chain polymer comprises ~he reaction product of at least one thermoplastic polymer capable of reaction with an epoxy or isocyanate functionality and at least one branching agent selected from the group consisting of epoxy containing at least two epoxy groups peT molecule of epoxy branching agent and isocyanate containing greater than two isocyanate groups per molecule of isocyanate branching agent.
The present invention further provides a branched chain, improved melt stTength thermoplastic polyester suitable for extrusion applications and having a melt strength ratio of Tl/T2 of less than about 1.6 at 235C wherein said branched chain ther plastic polyester CompTises the reaction pToduct of from about 95 to about 99% by weight of at least one saturated ~hermo-plastic polyester having carboxylic acid end functional groups and capable o~ reaction with an epoxy or isocyanate functionality, and from about l to about 5% by weight of at least one branching agent selected from the group consisting of epoxy containing at least two epoxy groups per lecl~le of epoxy branching agent and iso yanate containing greater than two isocyanate gxoups per molecule of isocyanate branching agent.
The eSseDCe of the present invention is the discovery that when thermoplastic polymers in a molten state are chemically reacted with the particularly defined epoxy or isocyanate branching agents as described above, the molten, the~moplastic polymer product possesses increased melt strength.
The polymers prepared according to the process of the present invention also have improved die swell characteristics, i.e., a~ter extrusion of the -6a-., .~, ~ ;5i36 molten polymer through an orifice having a particular diameter, the diameter of -the extruded polymer may increase up to about -two or three times the diameter of the extrusion orifice.
Description of the Preferred Embodiments As indicated hereinabove, the process of the present invention comprises reacting molten polymer with an epoxy or isocyanate branching agent to form an improved polymer having increased melt strength.
Any thermoplastic polymer which contains functional groups capable of reacting with the epoxy or isocyanate branching agent may be used in the process of the present invention. Such functional groups include carboxyl, amine, hydroxyl, epoxy, and isocyanate groups. Thermoplastic polymers include polyesters, polyamides, and allyl alcohol/styrene copolymers. Saturated thermoplastic polyesters are preferred.
The term "thermoplastic" polyrner is meant to incluae all polymers which soften when exposed to sufficient heat and which return to their original condition when cooled to room temperature.
Thermoplastic polyesters are preferred polymers for use in the present process. Saturated thermoplastic polyesters are particularly preferred and include saturated aliphatic/aromatic polyesters and wholly aromatic polyesters. The term "saturated"
polyester is meant to include all polyesters which do not contain ethylenic unsaturation in the polymer chain. The saturated, thermoplastic polyesters may be halogenated, i.e., contain halogen (e.g., bromine and/or chlorine) substitution in the polyester chain. The use of halogenated polyesters is particularly desirable when products having decreased flammability are desired.
iS36 The saturated thermoplastic polyesters useful in the present invention may be formed in a multitude of ways well kno~
to those skilled in this art. These saturated thermoplastic polyesters may be prepared from dihydric alcohols and dicarboxylic acids or the dialkyl esters of dicarboxylic acids wherein the alkyl groups may contain from one to seven carbon atoms.
Typical dihydric alcohols include aromatic dihydric alcohols such as bisphenol A [i.e., 2,2-bis(4-hydroxyphenyl)propane], phenolphthalein, 4,4'-sulfonyl diphenol,resorcinol, hydroquinone, catechol, naphthalene diols, stilbene bisphenol, 4,4'-diphenylether diphenol, and mixtures thereof, and aliphatic dihydric alcohols such as saturated dihydric alcohols having from 2 to 4 carbon atoms, and mixtures thereof.
Halogenated dihydric alcohols may also be employed.
Suchhal0genated dihydric alcohols include, for example, tetrabromobisphenol A, tetrachlorobisphenol A, 2,2'-[isopropyli-denebis(2,6-dichloro-p-phenylene)], and 2,2-bis[3,5-dibromo-4-(2-hydroxyethoxy)phenyl]propane.
Typical aromatic carboxylic acids include, for example, phthalic acid (including isophthalic and terephthalic), hydroxy-benzoic acid, and mixtures thereof.
Typical polyesters useful herein include the linear polyesters of an aromatic dicarboxylic acid reacted with a saturated aliphatic or cycloaliphatic diol~ particularly poly~
ethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, poly-1,3-cyclobutane terephthalate, polypentylene terephthalate, polycyclohexane-1,4-dimethylol terephthalate, poly-1,5-pentane diol terephthalate, and polyneopentylglycol terephthalate.
3~i Typical wholly aromatic thermoplastic polyesters incluae the reaction product of bisphenol A, isophthalic or terephthalic acids or mixtures (50/50 or 60/40 mole %) of isophthalic and terephthalic acids. Such polyesters may additionally contain minor amounts of a saturated aliphatic dihydric alcohol having from 2 to 4 carbon atoms. Halogenated wholly aromatic thermo-plastic polyesters include for example, the-reaction product of tetrabromobisphenol A, and a 50-50 mole ratio of isophthalic and terephthalic acid (and optionally, a minor amount of ethylene glycol).
Polypropylene terephthalate, polybutylene terephthalate, and mixtures thereof as well as mixtures of polyethylene terephthalate and polybutylene terephthalate are particularly preferred polyesters.
In the process of the present invention, the thermoplastic polymer is reacted with an epoxy branching agent containing at least two epoxy groups per molecule of epoxy branching agent or with an isocyanate branching agent containing greater than two isocyanate groups per mo]ecule of isocyan~te branching agent whereby high melt strength, substantially non-cross lin~ed thermoplastic polymers are formed.
Epoxy branching agents useful in the present invention include epoxy molecules having two or more epoxy groups per epoxy molecule. Thus, di-, tri-, or more highly substituted epoxies may be used. Halogenated epoxies (i.e., those substituted with e.g., bromine and/or chlorine) may also be used, especially ,~,",' ~
, i53~i when flame retardant properties are desired. Mixtures of two or more epoxies may be used as well as epoxies containing minor (i.e., less than about 25% by weight) amounts of impurities as long as the impurities do not affect the reaction between the thermoplastic polymer and the epoxy.
The epoxy resins utilized in the present invention are most commonly prepared by the condensation of bisphenol A
(4,4'-isopropylidene diphenol) and epichlorohydrin. Also, other polyols, such as aliphatic glycols and novolac resins may be reacted with epichlorohydrin for the production of epoxy resins suitable for use in the instant process provided resinous products are selected which possess the requisite flow properties.
In a preferred embodiment of the invention epoxy resins are selected which possess terminal epoxide groups and are condensation products of bisphenol A and epichlorohydrin of the following formula:
c~2~~c~_c~o~l~ -~ - t where n varies between zero and a small number less than about 10. When n is zero, the resin is a very fluid light-colorea material which is essentially the diglycidyl ether of bisphenol A. As the molecular weight increases, the viscosity of the resin also generally increases. Accordingly, the particularly preferred liquid epoxy resins generally possess an n value averaging less than about 1Ø Epoxy novalacs, as well as epoxy cycloaliphatics may also be selected. Illustrative examples by standard trade designations of particularly useful commercially available epoxy resins include: Epi-Rez* 508, Epi-Rez* 510, Epi-Rez* 520, Epi-Rez* 530, Epi-Rez* 540, Epi-Rez* 550, and Epi-Rez*
5155 (Celanese Coatings Company); DER* 332, and DE~T* 438 (Dow Chemical Company); Epon* 828, and Epon* 1031 (Shell Chemical Company); and ERLA* 2256 (Union Carbide). Other epoxies useful in the present process include cyclohexane diepoxide, cyclopentane diepoxide, and butane diol diglycidyl ether.
A particularly preferred epoxy isthe diglycidyl ether of bisphenol A.
Polyisocyanates useful in the present invention contain greater than two isoscyanate groups per molecule and thus include tri-, tetra-, and pentaisocyanates. Typical polyisocyanates include polyphenylene polyisocyanate, triphenylmethane triisocyanate, benzene triisocyanate, aliphatic and cyclo-aliphatic polyisocyanates, and naphthalene triisocyanate.
A particularly preferred polyisocyanate is polyphenylene poly-isocyanate.
Mixtures of two or more branching agents may be used as long as the particular branching agents in the mixture are compatible with each other --i.e., do not reduce reactivity or branching.
*Trademark; epoxy resin - 11 -. . .
.~!
;S36 The amounts of thermoplastic polymer and epoxy orisocyanate branching agent used in the present invention may vary widely, although generally from about 75 to about 99.99, typic-ally from about 90 to about 99.9, and preferably from about 95 to about 99% by weight polymer, and generally from about 0.01 to about 25, typically from about 0.1 to about 10, and preferably from about 1 to about 5% by weight branching agent may be employed. The expressed percentages are by weight of the total reaction mixture (i.e., total weight of thermoplastic polymer and branching agent).
Other additives, both polymeric and non-polymeric, such as flame retardants, lubricity agents, dyes, antioxidants, and inorganic fillers (such as glass) may be employed as long as these additives do not interfere with the reaction between the thermoplastic polymer and the branching agent. Such additives may generally be present in amounts up to about 10 by weight of the total reaction mixture.
When an epoxy branching agent is employed in the present invention, it is necessary to add to the reaction mixture a catalyst or reaction initiator. Such catalysts or reaction initiators include aliphatic and aromatic amines, particularly tertiary amines, amine adducts, acids, acid anhydrides, aldehyde condensation products, and Lewis acid type catalysts, such as boron trifluoride. Particularly preferred catalysts or reaction initiators which produce improved products are disclosed in copending Canadian patent application Serial No. 266,401 (corresponding to United States Patent No. 4,101,601, issued on July 18, 1978).
. ~ ~12 ;536 When an isocyanate branching agent is employed in tbe present in-vention, a catalyst or reaction initiator is not generally needed since such reactions proceed at an acceptable rate in the absence of catalysts.
The thermoplastic polymer and branching agent may be blended in any convenient manner as long as they are in contact for a period of time suffi-cient for chemical reaction to take place. Thus, the improved melt strength ; polymers of the present invention may be prepared by coating the thermoplastic polymer with a solution of the branching agent in a soivent in which the branching agent is soluble and the polymer is insoluble. The solvent should be substantially non-reactive toward the reactants and products of the reac-tion. Such solvents include hydrocarbons (such as methylene chloride) and ketones. The coated polymer may be allowed to air dry and then may be heated to the temperature at which reaction between the thermoplastic polymer and branching agent takes place.
The reactants may also be prepared by blending the branching agent with solid polymer chip and then feeding this mixture to a melt screw extruder (such as a Werner-Pfleiderer ZSK twin screw extruder) which is at a temper-ature high enough to cause the polymer to melt and thus enable reaction be-tween the thermoplastic polymer and branching agent to take place.
Alternatively, the thermoplastic polymer may be milled until fully rnolten in a plastograph (such as a C.W. Brabender Rolle Type plastograph) at temperatures high enough to melt the polymer. When the polymer is in the molten state, the branching agent may be introduced directly into the polymer until a melt viscosity of generally greater than about 10,000, typically greater than about 20,000, and preferably greater than about 60,000 poise is achieved.
~; In this specification, the term "melt viscosity" refers to the viscosity of the polymer in a molten or fused state. Melt viscosity - is measured by dyna~ic viscosity evaluation in a rheometrics viscometer 30 at 240 C. Such a measurement may be obtained by placing a sample in a rheo-lC,~6~3~
meter and heating to 240C. The melt viscosity may be obtained by plotting dynamic viscosity versus frequency.
The present process may be carried out at subatmospheric, atmos-pheric, or superatmospheric pressures, al-though substantially atmospheric pressures are preferred.
The present process may be carried out at any temperature which is such that the thermoplastic polymer will remain in the molten sta-te for a period of time sufficient to enable reaction between the thermoplastic polymer and the branching agent to take place. However, the temperature should not be high enough to decompose the thermoplastic polymer. At atmospheric pres-sure, the reaction may be carried out a-t temperatures of generally from about 150 to about 350, typically from about 180 to about 300, and preferably from about 220 to about 280 C.
The reaction between the thermoplastic polymer and the branching agent may be conducted generally in any environment. However, because of the sensitivity of certain branching agents, catalysts, and polymers to the pres-ence of water, the reaction is preferably carried out in the substantial absence of water. Sufficient quantities of water tend -to destroy the activity of certain catalysts as well as tha-t of certain of the branching agents, and to degrade the polymers. It is also often desirable to conduct the reaction in the substantial absence of oxygen gas. Thus, the reaction is preferably carried out in dry nitrogen, helium, and/or argon.
The molten thermoplastic polymer and the branching agent must be in contact for a sufficient period of time for chemical reaction to take place. ~eaction progress may be monitored in various ways. For example, when polyesters or polymers containing carboxylic acid end groups are reacted with the branching agent, the progress of the reaction may be monitored by observing the decrease in the carbo~Jlic acid end groups (CEG) with time.
When no further decrease in CEG takes place, reaction has ceased.
P~eaction rate, of course, is a function of temperature, but in the ~653~i present invention a reaction time of generally from about 45 to about 150, typically from about 60 to about 130, preferably from about 90 to about 120 seconds (melt screw extruder) may be employed. Because mixing does not take place to as great a degree in a plastograph as in a melt screw extruder, re-action times in a plastograph are generally somewhat longer. When an epoxy branching agent is employed in the absence of a catalyst, significantly longer reaction times are required.
The process of the present invention may be carried out in a batch, semi-continuous, or continuous manner, as desired.
It should be noted that in the process of the present invention, a chemical reaction is actually occurring between the thermoplastic polymer and the branching agent. This reaction is evidenced by an increase in melt strength as well as an increase in the intrinsic viscosity (I.V.). When polyesters or compounds containing carboxylic acid end groups are reacted with the branching agents, the chemical reaction is also evidenced by a con-comitant decrease in CEG level.
The increase in melt strength and concomitant increase in I.V. re-sult from chain branching of the thermoplastic polymer, ~Jhich chain branching occurs when the polymer and branching agent are reacted as described herein-above.
As indicated hereinabove, the present process provides thermo-plastic polymers having increased melt strength. These increased melt strength thermoplastic polymers are useful for extrusion applications. Such applications include pipe, film, and blow molding uses such as inblow mold-ing bottles.
Melt strength may be measured by extruding a six-inch strand of thermoplastic polymer through a constant drive index apparatus at a temper-ature high enough to keep the polymer molten (generally about 235 C). Melt strength (~S) may be defined as follows:
~1 , ....
~96536 MS
wherein the time required to extrude a polymer s-trand three inches (Tl) from the base of the melt index barrel i5 determined and without interruption the time required to extrude the same polymer to six inches is determined. The difference between the total time at six inches and the time at three inches is computed to give T2.
A melt strength value of from about l.0 to about 2.6 is desirable when the material is to be used in extrusion applications. Ideally, a value of l.0 is desired since this would mean that the second three-inch segment extruded at the same rate as the first segment.
For polymers with poor or low melt strengths, the second segment is extruded much more rapidly than the firs-t segment, resulting in a Tl/T2 ratio significantly greater than lØ
Thus, polymers having poor or very low melt strengths have rather large values of Tl/T2. By saying that certain polymers have "no melt strength" is meant that the second segment of the six-inch strand is extruded so rapidly that T2 cannot be measured.
The term "high melt strength polymers" refers to polymers having a ratio of Tl/T2 approaching the ideal value of l.0, and the terms "poor" or "low melt strength polymers" refer to polymers having comparatively large Tl/T2 ratios. Polymers having "no melt strength" have so small a T2 value ;~ that the melt strength cannot be measured.
The melt strength of a polymer depends upon the particular polymer ; employed as well as the temperature. However, the improved melt strength polymers of the present invention have melt strengths of generally less than about 2.0, typically less than about 1.8, and preferably less than about 1.6 at 235C.
The improved melt strength polymers of the present invention also have improved die swell characteristics. Die swell may be described as the , ~ , 653~
increase in diameter which takes place when the molten polymer is released from an extrusion die. As the polymer moves through the die, the entangle-ments and branches of the polymer chains are deformed or displaced from their equilibrium positions. This represents a storage of elastic energy. As the polymer is released from the die, this energy is regained by a return of the entanglements and branches to their equilibrium positions. This results in die swell.
The diameter of the improved melt strength polymers of the present invention may increase up to about -two or three times the diameter of the ex-trusion orifice. Die swell is important for blow molding applications since(a) the larger the diameter of the extruded polymer, the easier it is for air to be blown into the melt, and (b~ the greater the die swell, the greater the expansion of the polymer to fit the particular mold.
The improved melt strength polymers of the present invention also have increased intrinsic viscosities. The "intrinsic viscosity" of the poly-mers of the present invention may be conveniently determined by the equation I.V. = lim In c~o c wherein Nr is the "relative viscosity" obtained by dividing the viscosity of a dilute solution of the polymer by the viscosity of the solvent employed (measured at the sarne temperature)~ and c is the polymer concentration in the solution, expressed in grams per 100 milliliters. The intrinsic viscosity of the improved polymers of the present invention in o-chlorophenol at 25 C is generally from about o.85 to about 1.7, -typically from about 0.90 to about 1.65 and preferably from about 0.95 to about 1.6 poise.
As indicated hereinabove, when polyesters or polymers containing carboxylic acid end groups are reacted with the branching agents, the extent of reaction may be determined by measuring the change in the number of micro-equivalents of carboxylic acid end groups per gram of polymer. By "carbox-ylic acid end groups" is meant the number of carboxylic acid end groups @~
~96536 present in the polymer, measured in microequivalents per gram of pol~Jmer.The number of carboxylic acid end groups may be measured by dissolving the polymer in a 70/30 mixture of o-cresol/chloroform solvent and potentiometri-cally titrating the solution with tetrabutylarnmonium hydroxide. When poly-esters or polymers containing carboxylic acid end functional groups are re-acted with the branching agent, these improved melt strength polymers may contain generally less than about 65, typically less than about 60, and pref-erably less than about 55 microequivalents of carboxylic acid end groups per gram of polymer.
The present invention is further illustrated by the following ex-amples. All parts and percentages in the examples as well as in the speci-fication and claims are by weight unless otherwise specified.
EXA~LE I
This Example illustrates the preparation of a highly branched, thermoplastic polyester useful in blow molding.
Forty-seven and one-half grams (95 weight percent) of polybutylene terephthalate having 62 milliequivalents of carboxylic acid end groups per kilogram of polybutylene terephthalate are added to a C.W. Brabender Rolle type plastograph. The polybutylene terephthalate is then heated to a temper-ature of 250 C such that only the molten polymer is present. At this time,
Polymers such as polyesters, polyamides, polyethers, and polyamines when melted generally form thin liquids naving low melt viscosities and poor melt strengths. These low melt viscosity materials are unsuited or are only poorly suited for the manufacture of extruded shapes, tubes, deep drawn articles, and large blow molded articles. In order to overcome this disadvantage and to convert these polymers to a form better suited for the above-mentioned manufacturing techniques it is known to add compounds to the plastics which will increase their melt viscosities.
The materials which are added to increase the melt viscosity of the plastics are generally cross-linking agents, as described, for example, in United States Patent 3,378,532. Such cross-linking agents may be added during the condensation reaction by which the plastics are formed, and/or to the plastics after their formation (prior to, or during their melting). Examples of cross-linking agents which may be added to the plastics after their formation and before or after their melting in order to increase the melt viscosity include compounds containing at least two epoxy or isocyanate groups in the molecule, organic phosphorus compounds, peroxides, bishaloalkylaryl compounds, and polyesters o~ carbonic acid.
~ o~9~53'6 These known_cross linking agents which are added to increase the melt viscosity of the polymer are not completely satisfactory. They may, for instance, cause an excessively rapid and large increase in viscosity or form reaction products which have an adverse influence on the quality of the plastics.
Furthermore, the results obtained with the use of these known cross-linking agents are not always uniform or reproducible.
For example, when polyesters of carbonic acid are used to increase the melt viscosity, the degree of viscosity increase is generally dependent not only upon the amount of additive used but also upon its molecular weight and on the stage of the polycondensation reaction at which the addition takes place.
Besides having sufficient melt viscosity or "melt strength", polymers which are to be used in blow molding and related applications should also possess sufficient die swell, i.e., the molten polymer should expand as it is released from the extrusion die. This die swell is important for blow molding applications since (a) the larger the diame-ter of ; the extruded polymer, the easier it is for air to be blown into the parison, and (b) the greater the die swell the greater the expansion of-the molten polymer to fit the particular mold.
Polyesters having low intrinsic viscosities are particularly difficult to blow mold. The prior art illustrates the use of nurnerous additives to modify various properties of polyesters. For example~ United States Patent 3,376,272 discloses a processforthe preparation of branched chain, high molecular weight thermoplastic polyesters having a multiplicity of linear non-cross.ilinked polyester branched chains from dicarboxylic acid anhydrides, monoepoxides, and an alcohol compound by reacting these compounds at a temperature below 150C. However, 1~9~36 the polyesters described in this patent are formed from s.nhyariaes and are therefore not crystalline. Non-crystalline pol~Jmers tend to take longer time to set up in a mola and thus are not suitea or are only poorly suited for blow molding and related applica-tions.
As indicated above, compounds containing epoxy groups in the molecule have been used to increase the melt viscosity of polyesters (see, for example, United States Patent 2,830,031).
But although the use of epoxies as cross-linking agents for polyesters is known, little appears known about the use of epoxies as reactants which promote the branching (and hence increase the "melt strength") but not the cross-linking of polyesters.
United States Patent 3,547,873 disclosesthe prcduction of thermoplastic molding compositions from linear saturated polyesters and polyfunctional epoxides. This process, however, also yields products which lack the melt strength ana die swell necessary for blow molding applications.
Polyisocyanates have also been used to increase the melt viscosity of polymers such as polyesters. For example, United States Patent 2,333,639 aiscloses the reaction of low intrinsic viscosity, low molecular weight polyesters with polyisocyanates (e.g., a diisocyanate) at temperatures up to 300C to form higher intrinsic viscosity, higher molecular weight, fusible polyesters, but this process results in relatively low melting, linear, soft amorphous polyesters with poor melt viscosity and poor die swell properties.
gL~g~S36 United States Patent 3,304,286 discloses the xeaction of a poly-ester with a polyisocyanate such as diisocyanate. However, this process yields products having straight chain non-branched structures. These products thus lack the melt strength and die swell needed for blow molding applications.
Furthermore, United States Patent 3,692,744 discloses the pre-paration of polyester molding materials which can be injection lded by having present in the polyes~erifica~ion mixture, besides the terephthalic acid and diol con~onents, 0.05 to 3 moles percent, based upon the acid component, of a compound containing at leas$ three ester forming groups such as a polycarboxylic acid, a polyhydric alcohol, or a hydroxy carboxylic acid.
The use of epoxy or isocyanate compounds is not disclosed, however.
The search has continued foT improved processes for preparing polymers having increased melt strength. The present invention has resulted from that search.
It would be advantageous to avoid or substantially alleviate the above problems of the prior art.
In particular~ it would be advantageous to have a process for preparing impToved polymer compositions having improved melt strength and die swell characteristics.
It would be advantageous to have a process for preparing improved polymer compositions useful in blow molding and profile extrusion applications.
It would be advantageous to have the improved polymer compositions prepared by these processes.
It would also be advantageous to have an improved polymer molding pxocess utilizing these new polymers.
In one aspect, the present invention provides a process for pre-paring branched chain thermoplastic polymers having increased melt strength which are useful in ext~usion applications. This process comprises reacting at least one thermoplastic polymer which is in the molten state and which ~L~3~6~36 is capable of reaction with an epoxy or isocyanate functionality, wi~h at least one branching agent selected from the gTOUp consisting of epoxy con-taining at least two epoxy groups per molecule of epoxy branching agent, and isocyanate containing greater than two isocyanate groups per molecule of isocyanate branching agent, to produce branched chain thermoplastic polymers having a melt strength ratio of Tl/T2 of less than about 2.0 at 235 C.
In another aspect~ the pxesent in~ention provides the melt strength improved thernoplastic polymers produced by this process.
In still another aspect, there is provided an improved molding process which comprises ~orming a melt of the above-described melt strength improved thermoplastic polymer into a desi~ed article and cooling the molten polymer.
According to a particular embodiment of the present invention there is provided a process for preparing branched chain thermoplastic polyesters of incTeased melt strength useful in extIusion applications, which pTOCeSS
comprises reacting a~ least one thermoplastic polyester capable of reaction with an epoxy or isocyanate functionality, said polyester being in the molten state, with at least one branching agent selected from the group con-sisting of epoxy containing at least two epoxy groups per lecule of epoxy branching ag~nt and isocyanate containing greater than two isocyanate groups per molecule of isocyanate branching agent to pYo~uce said branched chain ther~oplastic polyesters having a melt strength ratio of Tl/T2 of less than about 1.8 at 235 C.
The present invention also provides a process for preparing branched chain polybutylene terephthalate having increased melt strength and useful in ex~rusion applications which process comprises reacting from about 95 to about 99% by weight polybutylene terephthalate in the molten state, with from about 1 to about 5% by weight of at least one branching agent selected from the group consisting of epoxy containing at least two epoxy groups per molecule of epoxy branching agent, and isocyanate containing ~ 653~
greater than two isocyanate groups per molecule of isocyanate branching a~ent wherein said reaction is carried out at a temperature of from about 220 to about 280C and at substantially atmospheric pressure to produce said branched chain polybutylene terephthalate having a melt strength ratio of Tl/T2 of less than about 1.6 at 235C.
The present invention according -to a further aspect provides a branched chain, improved melt strength thermoplastic polymer suitable fo~
extrusion applications and having a melt strength ratio of Tl/T2 of less than about 2.0 at 235C wherein said branched chain polymer comprises ~he reaction product of at least one thermoplastic polymer capable of reaction with an epoxy or isocyanate functionality and at least one branching agent selected from the group consisting of epoxy containing at least two epoxy groups peT molecule of epoxy branching agent and isocyanate containing greater than two isocyanate groups per molecule of isocyanate branching agent.
The present invention further provides a branched chain, improved melt stTength thermoplastic polyester suitable for extrusion applications and having a melt strength ratio of Tl/T2 of less than about 1.6 at 235C wherein said branched chain ther plastic polyester CompTises the reaction pToduct of from about 95 to about 99% by weight of at least one saturated ~hermo-plastic polyester having carboxylic acid end functional groups and capable o~ reaction with an epoxy or isocyanate functionality, and from about l to about 5% by weight of at least one branching agent selected from the group consisting of epoxy containing at least two epoxy groups per lecl~le of epoxy branching agent and iso yanate containing greater than two isocyanate gxoups per molecule of isocyanate branching agent.
The eSseDCe of the present invention is the discovery that when thermoplastic polymers in a molten state are chemically reacted with the particularly defined epoxy or isocyanate branching agents as described above, the molten, the~moplastic polymer product possesses increased melt strength.
The polymers prepared according to the process of the present invention also have improved die swell characteristics, i.e., a~ter extrusion of the -6a-., .~, ~ ;5i36 molten polymer through an orifice having a particular diameter, the diameter of -the extruded polymer may increase up to about -two or three times the diameter of the extrusion orifice.
Description of the Preferred Embodiments As indicated hereinabove, the process of the present invention comprises reacting molten polymer with an epoxy or isocyanate branching agent to form an improved polymer having increased melt strength.
Any thermoplastic polymer which contains functional groups capable of reacting with the epoxy or isocyanate branching agent may be used in the process of the present invention. Such functional groups include carboxyl, amine, hydroxyl, epoxy, and isocyanate groups. Thermoplastic polymers include polyesters, polyamides, and allyl alcohol/styrene copolymers. Saturated thermoplastic polyesters are preferred.
The term "thermoplastic" polyrner is meant to incluae all polymers which soften when exposed to sufficient heat and which return to their original condition when cooled to room temperature.
Thermoplastic polyesters are preferred polymers for use in the present process. Saturated thermoplastic polyesters are particularly preferred and include saturated aliphatic/aromatic polyesters and wholly aromatic polyesters. The term "saturated"
polyester is meant to include all polyesters which do not contain ethylenic unsaturation in the polymer chain. The saturated, thermoplastic polyesters may be halogenated, i.e., contain halogen (e.g., bromine and/or chlorine) substitution in the polyester chain. The use of halogenated polyesters is particularly desirable when products having decreased flammability are desired.
iS36 The saturated thermoplastic polyesters useful in the present invention may be formed in a multitude of ways well kno~
to those skilled in this art. These saturated thermoplastic polyesters may be prepared from dihydric alcohols and dicarboxylic acids or the dialkyl esters of dicarboxylic acids wherein the alkyl groups may contain from one to seven carbon atoms.
Typical dihydric alcohols include aromatic dihydric alcohols such as bisphenol A [i.e., 2,2-bis(4-hydroxyphenyl)propane], phenolphthalein, 4,4'-sulfonyl diphenol,resorcinol, hydroquinone, catechol, naphthalene diols, stilbene bisphenol, 4,4'-diphenylether diphenol, and mixtures thereof, and aliphatic dihydric alcohols such as saturated dihydric alcohols having from 2 to 4 carbon atoms, and mixtures thereof.
Halogenated dihydric alcohols may also be employed.
Suchhal0genated dihydric alcohols include, for example, tetrabromobisphenol A, tetrachlorobisphenol A, 2,2'-[isopropyli-denebis(2,6-dichloro-p-phenylene)], and 2,2-bis[3,5-dibromo-4-(2-hydroxyethoxy)phenyl]propane.
Typical aromatic carboxylic acids include, for example, phthalic acid (including isophthalic and terephthalic), hydroxy-benzoic acid, and mixtures thereof.
Typical polyesters useful herein include the linear polyesters of an aromatic dicarboxylic acid reacted with a saturated aliphatic or cycloaliphatic diol~ particularly poly~
ethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, poly-1,3-cyclobutane terephthalate, polypentylene terephthalate, polycyclohexane-1,4-dimethylol terephthalate, poly-1,5-pentane diol terephthalate, and polyneopentylglycol terephthalate.
3~i Typical wholly aromatic thermoplastic polyesters incluae the reaction product of bisphenol A, isophthalic or terephthalic acids or mixtures (50/50 or 60/40 mole %) of isophthalic and terephthalic acids. Such polyesters may additionally contain minor amounts of a saturated aliphatic dihydric alcohol having from 2 to 4 carbon atoms. Halogenated wholly aromatic thermo-plastic polyesters include for example, the-reaction product of tetrabromobisphenol A, and a 50-50 mole ratio of isophthalic and terephthalic acid (and optionally, a minor amount of ethylene glycol).
Polypropylene terephthalate, polybutylene terephthalate, and mixtures thereof as well as mixtures of polyethylene terephthalate and polybutylene terephthalate are particularly preferred polyesters.
In the process of the present invention, the thermoplastic polymer is reacted with an epoxy branching agent containing at least two epoxy groups per molecule of epoxy branching agent or with an isocyanate branching agent containing greater than two isocyanate groups per mo]ecule of isocyan~te branching agent whereby high melt strength, substantially non-cross lin~ed thermoplastic polymers are formed.
Epoxy branching agents useful in the present invention include epoxy molecules having two or more epoxy groups per epoxy molecule. Thus, di-, tri-, or more highly substituted epoxies may be used. Halogenated epoxies (i.e., those substituted with e.g., bromine and/or chlorine) may also be used, especially ,~,",' ~
, i53~i when flame retardant properties are desired. Mixtures of two or more epoxies may be used as well as epoxies containing minor (i.e., less than about 25% by weight) amounts of impurities as long as the impurities do not affect the reaction between the thermoplastic polymer and the epoxy.
The epoxy resins utilized in the present invention are most commonly prepared by the condensation of bisphenol A
(4,4'-isopropylidene diphenol) and epichlorohydrin. Also, other polyols, such as aliphatic glycols and novolac resins may be reacted with epichlorohydrin for the production of epoxy resins suitable for use in the instant process provided resinous products are selected which possess the requisite flow properties.
In a preferred embodiment of the invention epoxy resins are selected which possess terminal epoxide groups and are condensation products of bisphenol A and epichlorohydrin of the following formula:
c~2~~c~_c~o~l~ -~ - t where n varies between zero and a small number less than about 10. When n is zero, the resin is a very fluid light-colorea material which is essentially the diglycidyl ether of bisphenol A. As the molecular weight increases, the viscosity of the resin also generally increases. Accordingly, the particularly preferred liquid epoxy resins generally possess an n value averaging less than about 1Ø Epoxy novalacs, as well as epoxy cycloaliphatics may also be selected. Illustrative examples by standard trade designations of particularly useful commercially available epoxy resins include: Epi-Rez* 508, Epi-Rez* 510, Epi-Rez* 520, Epi-Rez* 530, Epi-Rez* 540, Epi-Rez* 550, and Epi-Rez*
5155 (Celanese Coatings Company); DER* 332, and DE~T* 438 (Dow Chemical Company); Epon* 828, and Epon* 1031 (Shell Chemical Company); and ERLA* 2256 (Union Carbide). Other epoxies useful in the present process include cyclohexane diepoxide, cyclopentane diepoxide, and butane diol diglycidyl ether.
A particularly preferred epoxy isthe diglycidyl ether of bisphenol A.
Polyisocyanates useful in the present invention contain greater than two isoscyanate groups per molecule and thus include tri-, tetra-, and pentaisocyanates. Typical polyisocyanates include polyphenylene polyisocyanate, triphenylmethane triisocyanate, benzene triisocyanate, aliphatic and cyclo-aliphatic polyisocyanates, and naphthalene triisocyanate.
A particularly preferred polyisocyanate is polyphenylene poly-isocyanate.
Mixtures of two or more branching agents may be used as long as the particular branching agents in the mixture are compatible with each other --i.e., do not reduce reactivity or branching.
*Trademark; epoxy resin - 11 -. . .
.~!
;S36 The amounts of thermoplastic polymer and epoxy orisocyanate branching agent used in the present invention may vary widely, although generally from about 75 to about 99.99, typic-ally from about 90 to about 99.9, and preferably from about 95 to about 99% by weight polymer, and generally from about 0.01 to about 25, typically from about 0.1 to about 10, and preferably from about 1 to about 5% by weight branching agent may be employed. The expressed percentages are by weight of the total reaction mixture (i.e., total weight of thermoplastic polymer and branching agent).
Other additives, both polymeric and non-polymeric, such as flame retardants, lubricity agents, dyes, antioxidants, and inorganic fillers (such as glass) may be employed as long as these additives do not interfere with the reaction between the thermoplastic polymer and the branching agent. Such additives may generally be present in amounts up to about 10 by weight of the total reaction mixture.
When an epoxy branching agent is employed in the present invention, it is necessary to add to the reaction mixture a catalyst or reaction initiator. Such catalysts or reaction initiators include aliphatic and aromatic amines, particularly tertiary amines, amine adducts, acids, acid anhydrides, aldehyde condensation products, and Lewis acid type catalysts, such as boron trifluoride. Particularly preferred catalysts or reaction initiators which produce improved products are disclosed in copending Canadian patent application Serial No. 266,401 (corresponding to United States Patent No. 4,101,601, issued on July 18, 1978).
. ~ ~12 ;536 When an isocyanate branching agent is employed in tbe present in-vention, a catalyst or reaction initiator is not generally needed since such reactions proceed at an acceptable rate in the absence of catalysts.
The thermoplastic polymer and branching agent may be blended in any convenient manner as long as they are in contact for a period of time suffi-cient for chemical reaction to take place. Thus, the improved melt strength ; polymers of the present invention may be prepared by coating the thermoplastic polymer with a solution of the branching agent in a soivent in which the branching agent is soluble and the polymer is insoluble. The solvent should be substantially non-reactive toward the reactants and products of the reac-tion. Such solvents include hydrocarbons (such as methylene chloride) and ketones. The coated polymer may be allowed to air dry and then may be heated to the temperature at which reaction between the thermoplastic polymer and branching agent takes place.
The reactants may also be prepared by blending the branching agent with solid polymer chip and then feeding this mixture to a melt screw extruder (such as a Werner-Pfleiderer ZSK twin screw extruder) which is at a temper-ature high enough to cause the polymer to melt and thus enable reaction be-tween the thermoplastic polymer and branching agent to take place.
Alternatively, the thermoplastic polymer may be milled until fully rnolten in a plastograph (such as a C.W. Brabender Rolle Type plastograph) at temperatures high enough to melt the polymer. When the polymer is in the molten state, the branching agent may be introduced directly into the polymer until a melt viscosity of generally greater than about 10,000, typically greater than about 20,000, and preferably greater than about 60,000 poise is achieved.
~; In this specification, the term "melt viscosity" refers to the viscosity of the polymer in a molten or fused state. Melt viscosity - is measured by dyna~ic viscosity evaluation in a rheometrics viscometer 30 at 240 C. Such a measurement may be obtained by placing a sample in a rheo-lC,~6~3~
meter and heating to 240C. The melt viscosity may be obtained by plotting dynamic viscosity versus frequency.
The present process may be carried out at subatmospheric, atmos-pheric, or superatmospheric pressures, al-though substantially atmospheric pressures are preferred.
The present process may be carried out at any temperature which is such that the thermoplastic polymer will remain in the molten sta-te for a period of time sufficient to enable reaction between the thermoplastic polymer and the branching agent to take place. However, the temperature should not be high enough to decompose the thermoplastic polymer. At atmospheric pres-sure, the reaction may be carried out a-t temperatures of generally from about 150 to about 350, typically from about 180 to about 300, and preferably from about 220 to about 280 C.
The reaction between the thermoplastic polymer and the branching agent may be conducted generally in any environment. However, because of the sensitivity of certain branching agents, catalysts, and polymers to the pres-ence of water, the reaction is preferably carried out in the substantial absence of water. Sufficient quantities of water tend -to destroy the activity of certain catalysts as well as tha-t of certain of the branching agents, and to degrade the polymers. It is also often desirable to conduct the reaction in the substantial absence of oxygen gas. Thus, the reaction is preferably carried out in dry nitrogen, helium, and/or argon.
The molten thermoplastic polymer and the branching agent must be in contact for a sufficient period of time for chemical reaction to take place. ~eaction progress may be monitored in various ways. For example, when polyesters or polymers containing carboxylic acid end groups are reacted with the branching agent, the progress of the reaction may be monitored by observing the decrease in the carbo~Jlic acid end groups (CEG) with time.
When no further decrease in CEG takes place, reaction has ceased.
P~eaction rate, of course, is a function of temperature, but in the ~653~i present invention a reaction time of generally from about 45 to about 150, typically from about 60 to about 130, preferably from about 90 to about 120 seconds (melt screw extruder) may be employed. Because mixing does not take place to as great a degree in a plastograph as in a melt screw extruder, re-action times in a plastograph are generally somewhat longer. When an epoxy branching agent is employed in the absence of a catalyst, significantly longer reaction times are required.
The process of the present invention may be carried out in a batch, semi-continuous, or continuous manner, as desired.
It should be noted that in the process of the present invention, a chemical reaction is actually occurring between the thermoplastic polymer and the branching agent. This reaction is evidenced by an increase in melt strength as well as an increase in the intrinsic viscosity (I.V.). When polyesters or compounds containing carboxylic acid end groups are reacted with the branching agents, the chemical reaction is also evidenced by a con-comitant decrease in CEG level.
The increase in melt strength and concomitant increase in I.V. re-sult from chain branching of the thermoplastic polymer, ~Jhich chain branching occurs when the polymer and branching agent are reacted as described herein-above.
As indicated hereinabove, the present process provides thermo-plastic polymers having increased melt strength. These increased melt strength thermoplastic polymers are useful for extrusion applications. Such applications include pipe, film, and blow molding uses such as inblow mold-ing bottles.
Melt strength may be measured by extruding a six-inch strand of thermoplastic polymer through a constant drive index apparatus at a temper-ature high enough to keep the polymer molten (generally about 235 C). Melt strength (~S) may be defined as follows:
~1 , ....
~96536 MS
wherein the time required to extrude a polymer s-trand three inches (Tl) from the base of the melt index barrel i5 determined and without interruption the time required to extrude the same polymer to six inches is determined. The difference between the total time at six inches and the time at three inches is computed to give T2.
A melt strength value of from about l.0 to about 2.6 is desirable when the material is to be used in extrusion applications. Ideally, a value of l.0 is desired since this would mean that the second three-inch segment extruded at the same rate as the first segment.
For polymers with poor or low melt strengths, the second segment is extruded much more rapidly than the firs-t segment, resulting in a Tl/T2 ratio significantly greater than lØ
Thus, polymers having poor or very low melt strengths have rather large values of Tl/T2. By saying that certain polymers have "no melt strength" is meant that the second segment of the six-inch strand is extruded so rapidly that T2 cannot be measured.
The term "high melt strength polymers" refers to polymers having a ratio of Tl/T2 approaching the ideal value of l.0, and the terms "poor" or "low melt strength polymers" refer to polymers having comparatively large Tl/T2 ratios. Polymers having "no melt strength" have so small a T2 value ;~ that the melt strength cannot be measured.
The melt strength of a polymer depends upon the particular polymer ; employed as well as the temperature. However, the improved melt strength polymers of the present invention have melt strengths of generally less than about 2.0, typically less than about 1.8, and preferably less than about 1.6 at 235C.
The improved melt strength polymers of the present invention also have improved die swell characteristics. Die swell may be described as the , ~ , 653~
increase in diameter which takes place when the molten polymer is released from an extrusion die. As the polymer moves through the die, the entangle-ments and branches of the polymer chains are deformed or displaced from their equilibrium positions. This represents a storage of elastic energy. As the polymer is released from the die, this energy is regained by a return of the entanglements and branches to their equilibrium positions. This results in die swell.
The diameter of the improved melt strength polymers of the present invention may increase up to about -two or three times the diameter of the ex-trusion orifice. Die swell is important for blow molding applications since(a) the larger the diameter of the extruded polymer, the easier it is for air to be blown into the melt, and (b~ the greater the die swell, the greater the expansion of the polymer to fit the particular mold.
The improved melt strength polymers of the present invention also have increased intrinsic viscosities. The "intrinsic viscosity" of the poly-mers of the present invention may be conveniently determined by the equation I.V. = lim In c~o c wherein Nr is the "relative viscosity" obtained by dividing the viscosity of a dilute solution of the polymer by the viscosity of the solvent employed (measured at the sarne temperature)~ and c is the polymer concentration in the solution, expressed in grams per 100 milliliters. The intrinsic viscosity of the improved polymers of the present invention in o-chlorophenol at 25 C is generally from about o.85 to about 1.7, -typically from about 0.90 to about 1.65 and preferably from about 0.95 to about 1.6 poise.
As indicated hereinabove, when polyesters or polymers containing carboxylic acid end groups are reacted with the branching agents, the extent of reaction may be determined by measuring the change in the number of micro-equivalents of carboxylic acid end groups per gram of polymer. By "carbox-ylic acid end groups" is meant the number of carboxylic acid end groups @~
~96536 present in the polymer, measured in microequivalents per gram of pol~Jmer.The number of carboxylic acid end groups may be measured by dissolving the polymer in a 70/30 mixture of o-cresol/chloroform solvent and potentiometri-cally titrating the solution with tetrabutylarnmonium hydroxide. When poly-esters or polymers containing carboxylic acid end functional groups are re-acted with the branching agent, these improved melt strength polymers may contain generally less than about 65, typically less than about 60, and pref-erably less than about 55 microequivalents of carboxylic acid end groups per gram of polymer.
The present invention is further illustrated by the following ex-amples. All parts and percentages in the examples as well as in the speci-fication and claims are by weight unless otherwise specified.
EXA~LE I
This Example illustrates the preparation of a highly branched, thermoplastic polyester useful in blow molding.
Forty-seven and one-half grams (95 weight percent) of polybutylene terephthalate having 62 milliequivalents of carboxylic acid end groups per kilogram of polybutylene terephthalate are added to a C.W. Brabender Rolle type plastograph. The polybutylene terephthalate is then heated to a temper-ature of 250 C such that only the molten polymer is present. At this time,
2.5 grams (5 weight percent) of the diglycidyl ether of bisphenol-A are added. After 30 minutes, the molten polybutylene terephthalate is removed from the plastograph and cooled to room temperature.
The melt viscosity of the unmodified polybutylene terephthalate as measured by a rheometer is 1,000 poise and the molecular weight is 44,168.
The melt viscosity of the polybutylene terephthalate as modified by the di-glycidyl ether of bisphenol-A is go,oob poise and its molecular weight is 44,870. The modified polybutylene terephthalate is fusible and substantially thermoplastic.
A cornparison of the intrinsic viscosity (I.V.), n~ber of csrbox-~/
5~i ylic acid end groups (CEG), and melt strength (MS) of bot~l t'ne unmodifiea ana modifiea polybutylene terephthalate (PBT) is inaicatea in Table I below:
TABLE I
-Property Unmodified PBT Modified PBT
I.V. 0.75 0.97( ) C.E.G. 85 50 M.S. not measurable ( ) 1.5 (1) The present invention also provides a method for increasing the I.V. of PBT as indicated by the increase from 0.75 to 0.97 when modified with the branching agent.
(2) MS could not be measured in this case because the molten polymer had such a poor MS that it drippea.
EXAMPLE II
This Example illustrates the preparation of a highly branchea, thermoplastic polyester useful in blow molding, using polyethylene terephthal-ate reacted with polyphenylene polyisocyanate.
; Forty-eight grams of polyethylene terephthalate having 60 milli-equivalents of carboxylic acid end groups per kilogram of polyethylene tere-phthalate are adaed to a C.W. Brabenaer Rolle type plastograph. The poly-ethylene terephthalate is heatea to a temperature of 270 C such that only molten polymer is present. At this time, 2.0 grams of polyphenylene poly-;~ isocyanate (averaging more than two isocyanate groups per molecule) are added to the molten polyethylene terephthalate at 270C. After 5 minutes the molten ; 15 polyet'nylene terep'nthalate is removed from the plastograph and cooled to room temperature.
The melt viscosity of the unmodified polyethylene terephthalate is 9,000 poise and its molecular weight is 46,ooo whereas the melt viscosity of the polyet'nylene terephthala-te as modifiea in accordance with the process of the present invention is 98,ooo poise ana its molecular weight is ~7,200.
The modified polyethylene terephthala-te is fusible and substantially thermo-plastic.
,~, ;5;~6 A comparison of the I.V., CEG, and MS of both the unmodified and modified polyethylene terephthalate (PET) is indicated in Table II belou:
TABLE II
_ . _ . ... _ . _ . _ .
Property Unmodified PETModified PET
IV 1.0 1.2 ~S 4.6 1.1 EXAMPLE III
This Example illustrates the preparation of a bighly branched, thermoplastic polyester useful in blow molding, using polybutylene tere-phthalate reacted with triphenylmethane triisocyan-ate.
Forty-nine grams of polybutylene terephthalate having 65 milli-equivalents of hydroxyl end groups per kilogram are added to a C.W. Brabendar Rolle type plastograph. The polymer i8 heated to 250 C and when all the polymer is molten, one gram of triphenylmethane triisocyanate is added.
After seven minutes, the molten polymer is removed and cooled to room temper-ature.
The modified polybutylene terephthalate is fusible and substantially thermoplastic and has a melt viscosity of 95,000 poise and a molecular weight of 46,ooo. The melt viscosity of a polybutylene terephthalate formed in the same manner without the triphenylmethane triisocyanate branching agent has a melt viscosity of 1,000 poise and a molecular weight of 44,000.
A comparison of the I.V., CEG and MS of both the unmodified and modified PLT is indicated in Table III below:
TABLE III
Property Unmodified PBTModified PBT
IV O.gO 1.1 5.0 ~.2 _ 20 -~9~5~
E ~ ~LE IV
This Example illustrates the use of a catalyst (triphenyl pbos-phine) to increase the rate of the reaction of Example III.
The same procedure as in Example III is employed except that 0.5 grams of triphenyl phosphine are added to the molten polybutylene terephal-ate at the same -time as the triphenylmethane -triisocyanate. The same re-sults are obtained in half the reaction time.
EXAMPLE V
This Example illustrates the preparation of a highly branched, thermoplastic polyester useful in blow molding, by employing polybutylene terephthalate pellets coated with polyphenylene polyisocyanate.
Forty-nine grams of polybutylene terephthalate having 65 milli-equivalents of hydroxyl end groups per kilogram are coated with a solution of polyphenylene polyisocyanate in methylene chloride with the result that, when the methylene chloride is evaporated, there is provided polybutylene terephthalate pellets coated with about 1.5 weight percent polyphenylene polyisocyanate. These coated pellets are treated as in Exarnple III with similar results.
The polymer melts obtained in accordance with the present invention have a uniform viscosity of a sufficien-tly high value to be outstandingly suited for use in fabrication techniques for production of articles, as, for example, extrusion, particularly blow molding. With the use of tbe melt vis-cosity increasing additives in accordance with the presen-t invention~ an ex-cessively rapid increase in viscosity is avoided. Furthermore, the invention has the additional advantage that the additives used in accordance thereof are completely compatible with the polymers so that they distribute them-selves quite uniformly in the melted mass.
The polymers with the increased melt viscosity in accordance with the present invention may be worked up without difficulty into extruded shapes of all types, such as tubes or rods, into large blown bodies, as well /j ~L~96~i3~
as sheets for blow molding, vacuum molding, deep-drawing, ana the like.
The improved melt strength polymers of the present invention have improved tensile strength, percent elongation, flexural strength, flexural modulus, tensile modulus, and Rockwell hardness as indicated in Table IV
5 below (the polybutylene terephthalate is modified as in Example III).
TABLE IV
Property (1) Unmodified PBT Modified PBT
Tensile Strength 7400 790G
Percent Elongation 5.9 8.2 Flexural Strength 10,900 13,100 Flexural Modulus 3.72 x 105 4.19 X 105 Tensile Modulus 3.66 x 105 4.21 x 105 Rockwell Hardness-"m" 58 74 . .
(1) As determined on specimens which were injection molded on a 2.5 oz.
:~ Stubbe Screw injection molding machine under the conditions listed in Table V below:
TABLE V
Nozzle Temperature ( C) 241 Barrel Temperature ( C) 235 Mold Temperature (C) 54 RPM (Screw) 85 Cycle (Seconds) 22 - EXAMPLE VI
The various polyesters formed in Examples I to V are each utilized in the blow-molding of a 2.2 inch diameter, 3.3 inch high barrel shape aero-sol container.
Blow molding of melt viscosity increased polyesters is accomplished by cha-rging -the polymer to a 2.5 inch multi-station rotary blow molder at 241 C, and the pol~ner is processed under the conditions listed in Table VI
~Dg653~
below:
TABLE_VI
Screw (RPM) ~5 Back Pressure (psi) 1600 Blow Pressure (psi) 120 Cornpression Rate 3.5/1 The blow molded articles formed from the polyesters of Examples I
through V which have been modified with a branching agent are well-formed, of uniform thickness, have high gloss and no pitmarks. The blow molded articles formed from the various cornparative polyesters of the Examples which are not modified with the branching agent, however, are not blow moldable and conse-quently are poorly formed, have nonuniform walls, and are generally rather rough.
A comparison of the branched modified polyester of the present in-vention with unmodified (non-branched) polyesters with respect to certain properties of blow molded articles are given in Table VII below:
TABLE VII
Blow Molded Property Modified Polyester Unmodified Polyester Wall Thickness uniform variable Surface Gloss high low Internal Roughness none poor Pinch-Off Weld good poor Pitmarks none many Shape good poorly defined The principles, preferred embodiments, and modes of operation of the present invention have been described in the foregoing specification. The in-vention which is intended to be protected herein, however, is not to be con-strued as limited to the particular forms disclosed, since these are to be regarded as illustrative rather than restrictive. Variations and changes may be made by those skilled in the art without departing from the spirit of the invention.
The melt viscosity of the unmodified polybutylene terephthalate as measured by a rheometer is 1,000 poise and the molecular weight is 44,168.
The melt viscosity of the polybutylene terephthalate as modified by the di-glycidyl ether of bisphenol-A is go,oob poise and its molecular weight is 44,870. The modified polybutylene terephthalate is fusible and substantially thermoplastic.
A cornparison of the intrinsic viscosity (I.V.), n~ber of csrbox-~/
5~i ylic acid end groups (CEG), and melt strength (MS) of bot~l t'ne unmodifiea ana modifiea polybutylene terephthalate (PBT) is inaicatea in Table I below:
TABLE I
-Property Unmodified PBT Modified PBT
I.V. 0.75 0.97( ) C.E.G. 85 50 M.S. not measurable ( ) 1.5 (1) The present invention also provides a method for increasing the I.V. of PBT as indicated by the increase from 0.75 to 0.97 when modified with the branching agent.
(2) MS could not be measured in this case because the molten polymer had such a poor MS that it drippea.
EXAMPLE II
This Example illustrates the preparation of a highly branchea, thermoplastic polyester useful in blow molding, using polyethylene terephthal-ate reacted with polyphenylene polyisocyanate.
; Forty-eight grams of polyethylene terephthalate having 60 milli-equivalents of carboxylic acid end groups per kilogram of polyethylene tere-phthalate are adaed to a C.W. Brabenaer Rolle type plastograph. The poly-ethylene terephthalate is heatea to a temperature of 270 C such that only molten polymer is present. At this time, 2.0 grams of polyphenylene poly-;~ isocyanate (averaging more than two isocyanate groups per molecule) are added to the molten polyethylene terephthalate at 270C. After 5 minutes the molten ; 15 polyet'nylene terep'nthalate is removed from the plastograph and cooled to room temperature.
The melt viscosity of the unmodified polyethylene terephthalate is 9,000 poise and its molecular weight is 46,ooo whereas the melt viscosity of the polyet'nylene terephthala-te as modifiea in accordance with the process of the present invention is 98,ooo poise ana its molecular weight is ~7,200.
The modified polyethylene terephthala-te is fusible and substantially thermo-plastic.
,~, ;5;~6 A comparison of the I.V., CEG, and MS of both the unmodified and modified polyethylene terephthalate (PET) is indicated in Table II belou:
TABLE II
_ . _ . ... _ . _ . _ .
Property Unmodified PETModified PET
IV 1.0 1.2 ~S 4.6 1.1 EXAMPLE III
This Example illustrates the preparation of a bighly branched, thermoplastic polyester useful in blow molding, using polybutylene tere-phthalate reacted with triphenylmethane triisocyan-ate.
Forty-nine grams of polybutylene terephthalate having 65 milli-equivalents of hydroxyl end groups per kilogram are added to a C.W. Brabendar Rolle type plastograph. The polymer i8 heated to 250 C and when all the polymer is molten, one gram of triphenylmethane triisocyanate is added.
After seven minutes, the molten polymer is removed and cooled to room temper-ature.
The modified polybutylene terephthalate is fusible and substantially thermoplastic and has a melt viscosity of 95,000 poise and a molecular weight of 46,ooo. The melt viscosity of a polybutylene terephthalate formed in the same manner without the triphenylmethane triisocyanate branching agent has a melt viscosity of 1,000 poise and a molecular weight of 44,000.
A comparison of the I.V., CEG and MS of both the unmodified and modified PLT is indicated in Table III below:
TABLE III
Property Unmodified PBTModified PBT
IV O.gO 1.1 5.0 ~.2 _ 20 -~9~5~
E ~ ~LE IV
This Example illustrates the use of a catalyst (triphenyl pbos-phine) to increase the rate of the reaction of Example III.
The same procedure as in Example III is employed except that 0.5 grams of triphenyl phosphine are added to the molten polybutylene terephal-ate at the same -time as the triphenylmethane -triisocyanate. The same re-sults are obtained in half the reaction time.
EXAMPLE V
This Example illustrates the preparation of a highly branched, thermoplastic polyester useful in blow molding, by employing polybutylene terephthalate pellets coated with polyphenylene polyisocyanate.
Forty-nine grams of polybutylene terephthalate having 65 milli-equivalents of hydroxyl end groups per kilogram are coated with a solution of polyphenylene polyisocyanate in methylene chloride with the result that, when the methylene chloride is evaporated, there is provided polybutylene terephthalate pellets coated with about 1.5 weight percent polyphenylene polyisocyanate. These coated pellets are treated as in Exarnple III with similar results.
The polymer melts obtained in accordance with the present invention have a uniform viscosity of a sufficien-tly high value to be outstandingly suited for use in fabrication techniques for production of articles, as, for example, extrusion, particularly blow molding. With the use of tbe melt vis-cosity increasing additives in accordance with the presen-t invention~ an ex-cessively rapid increase in viscosity is avoided. Furthermore, the invention has the additional advantage that the additives used in accordance thereof are completely compatible with the polymers so that they distribute them-selves quite uniformly in the melted mass.
The polymers with the increased melt viscosity in accordance with the present invention may be worked up without difficulty into extruded shapes of all types, such as tubes or rods, into large blown bodies, as well /j ~L~96~i3~
as sheets for blow molding, vacuum molding, deep-drawing, ana the like.
The improved melt strength polymers of the present invention have improved tensile strength, percent elongation, flexural strength, flexural modulus, tensile modulus, and Rockwell hardness as indicated in Table IV
5 below (the polybutylene terephthalate is modified as in Example III).
TABLE IV
Property (1) Unmodified PBT Modified PBT
Tensile Strength 7400 790G
Percent Elongation 5.9 8.2 Flexural Strength 10,900 13,100 Flexural Modulus 3.72 x 105 4.19 X 105 Tensile Modulus 3.66 x 105 4.21 x 105 Rockwell Hardness-"m" 58 74 . .
(1) As determined on specimens which were injection molded on a 2.5 oz.
:~ Stubbe Screw injection molding machine under the conditions listed in Table V below:
TABLE V
Nozzle Temperature ( C) 241 Barrel Temperature ( C) 235 Mold Temperature (C) 54 RPM (Screw) 85 Cycle (Seconds) 22 - EXAMPLE VI
The various polyesters formed in Examples I to V are each utilized in the blow-molding of a 2.2 inch diameter, 3.3 inch high barrel shape aero-sol container.
Blow molding of melt viscosity increased polyesters is accomplished by cha-rging -the polymer to a 2.5 inch multi-station rotary blow molder at 241 C, and the pol~ner is processed under the conditions listed in Table VI
~Dg653~
below:
TABLE_VI
Screw (RPM) ~5 Back Pressure (psi) 1600 Blow Pressure (psi) 120 Cornpression Rate 3.5/1 The blow molded articles formed from the polyesters of Examples I
through V which have been modified with a branching agent are well-formed, of uniform thickness, have high gloss and no pitmarks. The blow molded articles formed from the various cornparative polyesters of the Examples which are not modified with the branching agent, however, are not blow moldable and conse-quently are poorly formed, have nonuniform walls, and are generally rather rough.
A comparison of the branched modified polyester of the present in-vention with unmodified (non-branched) polyesters with respect to certain properties of blow molded articles are given in Table VII below:
TABLE VII
Blow Molded Property Modified Polyester Unmodified Polyester Wall Thickness uniform variable Surface Gloss high low Internal Roughness none poor Pinch-Off Weld good poor Pitmarks none many Shape good poorly defined The principles, preferred embodiments, and modes of operation of the present invention have been described in the foregoing specification. The in-vention which is intended to be protected herein, however, is not to be con-strued as limited to the particular forms disclosed, since these are to be regarded as illustrative rather than restrictive. Variations and changes may be made by those skilled in the art without departing from the spirit of the invention.
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for preparing branched chain thermoplastic polymers of increased melt strength useful in extrusion applications, which process com-prises reacting at least one thermoplastic polymer capable of reaction with an epoxy or isocyanate functionality, said polymer being in the molten state, with at least one branching agent selected from the group consisting of epoxy containing at least two epoxy groups per molecule of epoxy branching agent and isocyanate containing greater than two isocyanate groups per molecule of isocyanate branching agent to produce said branched chain thermoplastic poly-mers having a melt strength ratio of T1/T2 of less than about 2.0 at 235°C.
2. The process of claim 1 wherein the branching agent is the digly-cidyl ether of p,p'-isopropylidenediphenol and wherein a tertiary amine cat-alyst is employed.
3. The process of claim 1 wherein the branching agent is polyphenyl-ene polyisocyanate.
4. The process of claim 1 wherein the polymer is a saturated thermo-plastic polyester and wherein from about 0.01 to about 25% by weight branch-ing agent is added to from about 75 to about 99.99% by weight of the polyester in the presence of a catalytic amount of an amine catalyst at a temperature above the melting point but below the decomposition temperature of the poly-ester.
5. A process for preparing branched chain thermoplastic polyesters of increased melt strength useful in extrusion applications, which process comprises reacting at least one thermoplastic polyester capable of reaction with an epoxy or isocyanate functionality, said polyester being in the molten state, with at least one branching agent selected from the group consisting of epoxy containing at least two epoxy groups per molecule of epoxy branching agent and isocyanate containing greater than two isocyanate groups per mol-ecule of isocyanate branching agent to produce said branched chain thermo-plastic polyesters having a melt strength ratio of T1/T2 of less than about 1.8 at 235°C.
6. The process of claim 5 wherein the reaction is carried out at a temperature of from about 150 to about 350°C and at substantially atmospheric pressure, and wherein from about 0.1 to about 10% by weight branching agent is added to from about 90 to about 99.9% by weight polyester, and wherein the branching agent is the diglycidyl ether of p,p'-isopropylidenediphenol.
7. The process of claim 5 wherein the branching agent is an epoxy and a tertiary amine catalyst is employed.
8. A process for preparing branched chain polybutylene terephthal-ate having increased melt strength and useful in extrusion applications which process comprises reacting from about 95 to about 99% by weight polybutylene terephthalate in the molten state, with from about 1 to about 5% by weight of at least one branching agent selected from the group consisting of epoxy con-taining at least two epoxy groups per molecule of epoxy branching agent, and isocyanate containing greater than two isocyanate groups per molecule of iso-cyanate branching agent wherein said reaction is carried out at a temperature of from about 220 to about 280°C and at substantially atmospheric pressure to produce said branched chain polybutylene terephthalate having a melt strength ratio of T1/T2 of less than about 1.6 at 235°C.
9. A branched chain, improved melt strength thermoplastic polymer suitable for extrusion applications and having a melt strength ratio of T1/T2 of less than about 2.0 at 235°C wherein said branched chain polymer comprises the reaction product of at least one thermoplastic polymer capable of reaction with an epoxy or isocyanate functionality and at least one branch-ing agent selected from the group consisting of epoxy containing at least two epoxy groups per molecule of epoxy branching agent and isocyanate containing greater than two isocyanate groups per molecule of isocyanate branching agent.
10. The branched chain, thermoplastic polymer composition of claim 9 wherein said branched chain, thermoplastic polymer is the reaction product of from about 75 to about 99.99% by weight thermoplastic polymer with from about 0.01 to about 25% by weight branching agent and wherein said branching agent contains halogen substitution, and said branched chain, thermoplastic polymer has a melt strength ratio of T1/T2 of less than about 1.8 at 235°C.
11. A branched chain, improved melt strength thermoplastic polyester suitable for extrusion applications and having a melt strength ratio of T1/T2 of less than about 1.6 at 235°C wherein said branched chain thermo-plastic polyester comprises the reaction product of from about 95 to about 99% by weight of at least one saturated thermoplastic polyester having car-boxylic acid end functional groups and capable of reaction with an epoxy or isocyanate functionality, and from about 1 to about 5% by weight of at least one branching agent selected from the group consisting of epoxy containing at least two epoxy groups per molecule of epoxy branching agent and isocyanate containing greater than two isocyanate groups per molecule of isocyanate branching agent.
12. An improved molding process which comprises forming the molten polymer of claim 9 into a desired article and cooling the molten polymer.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US66906676A | 1976-03-22 | 1976-03-22 | |
| US669,066 | 1976-03-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1096536A true CA1096536A (en) | 1981-02-24 |
Family
ID=24684866
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA271,939A Expired CA1096536A (en) | 1976-03-22 | 1977-02-16 | Polymers for extrusion applications |
Country Status (11)
| Country | Link |
|---|---|
| JP (1) | JPS52114687A (en) |
| AU (1) | AU2336877A (en) |
| BE (1) | BE852585A (en) |
| BR (1) | BR7701740A (en) |
| CA (1) | CA1096536A (en) |
| DE (1) | DE2711148A1 (en) |
| FR (1) | FR2345479A1 (en) |
| GB (1) | GB1578472A (en) |
| IT (1) | IT1074310B (en) |
| MX (1) | MX144313A (en) |
| NL (1) | NL7702404A (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5592758A (en) * | 1978-11-06 | 1980-07-14 | Toray Ind Inc | Resin composition |
| JPS55137154A (en) * | 1979-03-30 | 1980-10-25 | Toray Ind Inc | Polyester composition |
| DE3401345A1 (en) * | 1984-01-17 | 1985-07-25 | Chemische Werke Hüls AG, 4370 Marl | MOLDS BASED ON HIGH MOLECULAR POLY (ALKYLENE TEREPHTHALATES) |
| EP0317797A3 (en) * | 1987-11-27 | 1991-03-20 | General Electric Company | Preparation of linear polyester compositions via polyepoxide concentrate |
| GB2229187A (en) * | 1989-03-15 | 1990-09-19 | Ici Plc | High molecular weight polyethylene terephthalate in solution |
| US5324556A (en) * | 1992-05-08 | 1994-06-28 | Showa Highpolymer Co., Ltd. | Polyester blow-molded articles |
| EP0569153B1 (en) * | 1992-05-08 | 1999-10-06 | Showa Highpolymer Co., Ltd. | Polyester resin composition |
| KR20150047939A (en) * | 2013-10-25 | 2015-05-06 | 삼성정밀화학 주식회사 | Biodegradable polyester resin compound and foamed article obtained therefrom |
-
1977
- 1977-02-16 CA CA271,939A patent/CA1096536A/en not_active Expired
- 1977-02-18 GB GB692577A patent/GB1578472A/en not_active Expired
- 1977-03-07 NL NL7702404A patent/NL7702404A/en not_active Application Discontinuation
- 1977-03-14 JP JP2713277A patent/JPS52114687A/en active Pending
- 1977-03-15 DE DE19772711148 patent/DE2711148A1/en not_active Withdrawn
- 1977-03-17 BE BE175885A patent/BE852585A/en unknown
- 1977-03-17 IT IT2139177A patent/IT1074310B/en active
- 1977-03-18 AU AU23368/77A patent/AU2336877A/en not_active Expired
- 1977-03-18 MX MX16842377A patent/MX144313A/en unknown
- 1977-03-21 FR FR7708412A patent/FR2345479A1/en active Granted
- 1977-03-21 BR BR7701740A patent/BR7701740A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| BR7701740A (en) | 1978-01-24 |
| DE2711148A1 (en) | 1977-10-06 |
| FR2345479B1 (en) | 1980-03-07 |
| GB1578472A (en) | 1980-11-05 |
| MX144313A (en) | 1981-09-28 |
| AU2336877A (en) | 1978-09-21 |
| BE852585A (en) | 1977-09-19 |
| IT1074310B (en) | 1985-04-20 |
| JPS52114687A (en) | 1977-09-26 |
| NL7702404A (en) | 1977-09-26 |
| FR2345479A1 (en) | 1977-10-21 |
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