NL1002080C2 - Low mol.wt. unsatd. polyester resin compsn. for a sheet moulding cpd. - Google Patents

Abstract

A low mol.wt. unsatd. polyester resin compsn. for a sheet moulding cpd. comprises: (a) a low mol.wt. unsatd. polyester comprising a polycondensation product of a polyhydric alcohol and an ethylenically unsatd. polycarboxylic acid; and (b) unsatd. end caps which are able to block the polyester chain ends from complexing with thickening agents during maturation leading to low pressure moulding cpds., and are opt. able to react with the unsatd. polyester or an olefinically unsatd. monomer if present.

Description

Title: UNSATURATED POLYESTER RESINS

TECHNICAL FIELD

This development concerns unsaturated polyester resins.

This development also includes the use of these compositions for automotive applications.

In particular, this development concerns Plate Forming Compositions (SMCs) which require significantly less pressure during compression molding than normal formulations.

v 10 BACKGROUND ART

Polyester resin unsaturated compositions are increasingly used in the automotive industry as a Sheet Molding Composition (SMC) from which parts, particularly body parts, can be formed. The unsaturated polyester resin compositions, in addition to the unsaturated polyesters and monomer components, contain so-called "low-profile" additives, which are thermoplastic polymers, which serve to prevent unwanted shrinkage when the composition is formed into a thermally cured article.

Recent developments have greatly improved the surface of the resulting auto part. However, the search for further surface improvement continues. In addition, typical SMCs for automotive applications require expensive machining and relatively high molding pressures to successfully form large parts (e.g., hoods).

DESCRIPTION OF THE INVENTION We have now developed a polyester with either non-reactive or reactive unsaturated end groups. The preferred embodiment of this invention contains non-reactive end groups. The unsaturated end groups can be glycidyl ethers (such as glycidyl methacrylate or other acrylates), alcohols (such as hexanol, propylated - 2 * alkyl alcohol), or acids (such as stearic acid, octanoic acid). we have found that these polyester resins are very useful for low pressure SMC formations. Our findings show improvements of several orders of magnitude in the surface. Surface analysis resulted in Loria values of 36. Loria values of 50 to 70 are considered to be quite good for surface smoothness of molded auto parts. Lower values mean a smooth surface.

10

BEST EMBODIMENT OF THE INVENTION

The resin composition we have developed includes: (a) an unsaturated polyester comprising a polycondensation of dihydric alcohols and ethylenically unsaturated polycarboxylic acids; and (b) a reactive or non-reactive end group. When the end group is reactive, it can react with unsaturated polyester and any reactive monomer during curing. When non-reactive, it simply blocks the chain end 20 during the thickening reaction.

In the preferred embodiment of this invention, the end groups of glycidyl acrylates are represented by the formula: R 1 25 R 2 -O-C-OCH 2 wherein R 1. hydrogen or an alkyl radical of 1 to 5 carbon atoms, and R2 is a glycidyl ester group of the formula:

O

CH2-CH-CH2-; or O is CH2-CH-CH2-R3, wherein R3 ranges from C7H14O3- to C11H20O3-. Usually, R3 includes reaction products using 1,4-butanediol, neopentyl glycol, resorcinol, cyclohexane dimethanol and the like.

1 (> ft ', ·.!? F' - 3 -

Usually the glycidyl acrylates have the composition in which:

R 1 is hydrogen or an alkyl radical of 1 to 5 carbon atoms; R2 is C3H5O- to C14H25O4-; R3 is C7H14O3- to C11H20O3 ".

Preferred glycidyl acrylates are of the composition wherein:

R 1 is hydrogen or an alkyl radical of 1 to 3 carbon atoms 10; R2 is C3H5O- to C10H19O4-; R3 is ¢ 711 ^ 4 () 3- to C8H15O3.

The dihydridic alcohols of this invention are represented by the formula HO - (R40) x-OH

wherein R4 is an alkyl radical of 2-10 carbon atoms and X is an integer from 1 to 4.

Preferably we use dihydridic alcohols with alkyl groups of 2 to 5 carbon atoms. We also prefer glycols selected from a group of high performance glycols comprising neopentyl glycol (NPG), 1,4-cyclohexanedimethanol (CHDM), 2,2,4-trimethyl-1,3-pentanediol (1MPD), and 2-methyl-1,3-propanediol (MPD).

We prepared the polyesters in two steps, starting with the polyester condensation of one or more polybasic acids and one or more polyhydridic alcohols in a molar ratio of about 1: 1. Condensation is usually stopped at an unusually high acid value (50-80 mg KOH / g resin instead of the conventional 10-30 mg KOH / g resin). In the second step (post-polymerization functionalization), the residual acid groups of the polymer are subjected to a reaction with the epoxy group of the acrylate in a polybasic acid to acrylate ratio of about 2-10: 1. In this way, the acrylic is incorporated into the product.

In summary, we use the epoxide / acid reaction to bond the acrylic to the polyester.

t l ''; :; O 0 „1 - 4 -

In a second embodiment of the invention, we again prepared the polyesters in two steps, starting with the polyester condensation of one or more polybasic acids and one or more polyhydridic alcohols in a molar ratio of about 1: 1. After stopping the polycondensation at relatively high acid values (acid value of 50-80 mg KOH / g resin), we add an unsaturated monohydridic alcohol of the following formula: HO- (R5-0) y-CH = CH2 10 where R5 an alkyl radical having from 2 to 10 carbon atoms and Y being an integer from 1 to 4. Preferably we use monohydridic alcohols having alkyl groups having 2 to 6 carbon atoms. Sometimes at this point we add an esterification catalyst, such as dibutyltin oxide or the like. Final polycondensation lowers the acid value to the standard range of 10-30 mg KOH / g resin.

The unsaturated polyester includes the polycondensation product of one or more dihydric alcohols and one or more ethylenically unsaturated polycarboxylic acids. Polycarboxylic acid 20 usually refers to the poly or dicarboxylic acids or anhydrides, poly or dicarboxylic acid halides, and poly or dicarboxylic acid esters. Suitable unsaturated polycarboxylic acids, and the corresponding anhydrides and acid halides containing polymerization carbon-carbon double bonds, may include maleic anhydride, maleic acid or fumaric acid. A small portion of the unsaturated acid, up to about forty mole percent, can be replaced with di- or polycarboxylic acid that does not contain a polymerizable carbon-carbon bond. Examples thereof include O-phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, methyl succinic acid and the like. Dihydric alcohols useful in the preparation of the polyesters include 1,2-propanediol (hereinafter referred to as propylene glycol), dipropylene glycol, diethylene 35 glycol, 1,3-butanediol, ethylene glycol, glycerol and the like. Examples of suitable unsaturated polyesters are the polycondensation products of: I '...

- 5 - (1) propylene glycol and maleic acid and / or fumaric acid, (2) 1,3-butanediol and maleic acid and / or fumaric acid, (3) combinations of ethylene and propylene glycol (about 50 mole percent or less of ethylene glycol) and maleic acid and / or 5 fumaric acid, (4) propylene glycol, maleic acid and / or fumaric acid, and dicyclopentadiene reacted with water.

In another preparation of this invention, one or more polybasic acids and one or more polyhydridic alcohols are subjected to a reaction to form a polyester in a molar ratio of about 1: 1. In the second step, the residual acid groups of the polyester are subjected to a reaction with an unsaturated alcohol such as propoxylated alkyl alcohol and the like. In a third embodiment of the invention, a non-reactive end group is subjected to a reaction with the polyester in a one-step synthesis approach: one or more polybasic acids and one or more polyhydric alcohols react in the presence of one or more of the following following table taken (but not limited to 20) monofunctional compounds

Table I

Non-reactive end groups Carboxylic acids Benzoic acid 25 Stearic acid

Oleic acid

Cyciohexane carboxylic acid

Alcohols 30 Benzyl alcohol 2 -Ethylhexanol Cyclohexanol

Ethylene glycol mono-n-butyl ether Diethylene glycol mono-methyl ether 35 Diethylene glycol mono-ethyl ether

Diethylene glycol mono-n-butyl ether; o. 3f! - 6 -

The monomeric component of the resinous system includes materials that copolymerize with the unsaturated polyester. The ethylenically unsaturated monomer copolymerizable with the unsaturated polyester is usually styrene; although methylstyrene is also useful, as are acrylates and methacrylates such as methyl acrylates, ethyl acrylate, methyl methacrylate, ethyl methacrylate, etc.

The "low-profile" additive component of the resinous system includes thermoplastic polymers that cause phase separation and voiding, thus compensating for the polymerization shrinkage that usually occurs during curing. Low-profile additives are materials that, when mixed in an unsaturated polyester and cured, lead to a multi-phase system. Some polymers useful as "low-profile" additives include homopolymers and copolymers of acrylic and methacrylic acid esters, cellulose acetate butyrate, vinyl acetate homopolymers and copolymers, polyurethanes prepared from polyisocyanates, preferably diisocyanates, and polyether polyols, , polycaprolactone, styrene-butadiene copolymers, some modified celluloses, and certain alkyl oxide polymers. The above list of "low-profile" additives does not intend to include all "low-prof ile" additives, but is more intended to show examples of materials used to cause the multi-phase morphology present in "low-prof ile" resins.

The acid number to which the polymerizable unsaturated polyesters are condensed usually ranges from 30 to 80. The acid number preferably ranges from 40 to 70. The weight average molecular weight of the unsaturated polyester ranges from 500 to 5,000 g / mol. The weight average molecular weight preferably ranges from 1,000 to 4,000 g / mol.

The plate forming composition of this invention may also include other conventional materials. For example, conventional chemical thickeners can be physically mixed into the resin. The chemical thickeners usually include metal oxides, hydroxides, and alkoxides of Group II, III or IV of the Periodic System. Calcium oxide and magnesium oxide or the respective hydroxides 5 are most often used. In preferred embodiments, the thickener is present in amounts ranging from about 0.5 to about 6 parts by weight. The thickener is usually suspended in a carrier resin, as is known in the art. The support material includes a composition that does not react with the thickener such as, for example, polymethyl methacrylate, polyvinyl acetate, saturated or unsaturated polyesters, and similar materials. The carrier resin is present in amounts ranging from about 0.5 to 8 parts by weight based on one hundred parts of the system.

Catalysts may also be included in small amounts in the thermosetting polyester resins, which contain ethylenically unsaturated monomer to aid in curing or crosslinking the unsaturated polyester with the monomer. Such catalysts are known and can be used similarly in this invention to aid in the curing of the unsaturated polyester and the monomer mixed with the "low-profile" thermoplastic polymer. Typical catalysts include, for example, organic peroxide and peracids such as tertiary butyl perbenzoate, tertiary butyl peroctoate, benzoyl peroxide and the like. The amounts of catalyst can be varied with the formation process and, in a known manner, varied comparatively with the content and types of the inhibitors used. In preferred embodiments, the catalyst is present in amounts ranging from about 0.5 to 2.5 parts by weight based on one hundred parts of the system.

The curing of the composition is carried out under pressure and upon heating, usually in a closed, preferably overpressure-type molding. Mold release agents can be added to the compositions to perform their normal function, as is known in the art. In preferred embodiments, the xnal release agents are present in amounts ranging from about 0.5 to 6.0 parts by weight, based on one hundred parts of the four-component resin system.

Fibers, fillers and pigments normally added to the resin compositions can also do this when formulating the plate-forming composition of this invention. By reinforcing fibers or fiber reinforcements 10 are meant glass fibers in any form, such as glass fabric, chopped glass strands, chopped or continuous strand glass fiber mat; however, the terms also include reinforcing agents which may also be used if desired, such as asbestos, cotton, synthetic organic fibers and metals.

Fillers, usually inert, and inorganic material useful in the compositions include, for example, talc, clay, calcium carbonate, silica, calcium silicate, and the like. In preferred embodiments, the fillers are present in amounts ranging from about 165 to about 250 parts by weight based on one hundred parts of the system.

Examples of pigments include "carbon black", iron oxide, titanium dioxide and the like, as well as organic pigments. In preferred embodiments, the pigments are present in amounts ranging from about 0 to about 4 parts by weight based on one hundred parts of the four component resin system.

In one aspect of the present invention, the preparation of plate forming composition is carried out by mixing together a first portion comprising the unsaturated polyester, the "low-profile" additive, the monamer and the like additives as a catalyst, mold release agent, and fillers. This is commonly known in the industry as the A-side composition. The second portion 35 (commonly known as the B-side composition) includes the thickener and a carrier resin therefor, and such additives as pigments and mold release agents. In a 1 Ö 0 c l ·; i) - Another aspect of the invention, an additional or secondary monomer can be added to the B-side composition in which the thickener is suspended.

The additional monomer includes vinyl toluene or styrene and is present in amounts ranging from about 1 to 8 parts by weight based on one hundred parts of the four component resin system.

The plate forming composition of the present invention can be prepared by mixing the 10 components in a suitable device at temperatures that are conventional and known to those skilled in the art. Once the sheet forming composition is formulated, the composition can be formed into thermosetting articles of the desired shape. The actual forming cycle 15 will of course depend on the exact composition being formed. In preferred embodiments, suitable forming cycles are performed at temperatures ranging from about 250-350 ° F (121-177 ° C) for periods ranging from about 1/3 to about 5 minutes. The following compositions are provided to illustrate examples of the compositions of the present invention.

INDUSTRIAL APPLICABILITY Example I

In a 10-gallon stainless steel reactor suitable for polyester synthesis, we charged 16.1 kg of propylene glycol, 18.9 kg of maleic acid, and 14.0 g of a 10% solution of toluhydroquinone THQ. We heat the reactor to 205 ° C or 30 until the acid value reaches 45-60 mg KOH / g resin. Then we cooled the reactor to 120 ° C.

While keeping the molten polyester at 120 ° C, we added the following to the reactor: - Butylate hydroxytoluene 8.7 g 35 - Para-benzoquinone (PBQ inhibitor) 0.8 g - N, N-Dimethylbenzylamine «- 10 - ( DMBA; GMA addition catalyst) 34.7 g Glycidyl methacrylate (GMA reactive end group) 1600.0 g

We added GMA dropwise so as not to rise above 120 ° C after the addition was complete and then kept the reactor at 120 ° C for 0.5-1.0 hours.

To dilute we then added the resin at 120 ° C to the following mixtures: - Styrene (reactive diluent) 17.8 kg 10 - 3-Tert-butylhydroquinone (inhibitor) 2.12 g - PBQ (inhibitor) 0.8 g - Butylated hydroxyanisole (BHA; inhibitor) 2,6-di-tert-butyl-4-methoxyphenol 1.25 g.

Example II

Low viscosity, high reactive chain ends unsaturated polyesters of Example I successfully make the following SMC composition for excellent surface.

Ingredient Weight (g) comment 20 Resin 2.709 Unsaturated polyester

of Example I.

LPA 1,144 Polv (ethylene glycol-co-propylene glycol-co-adipic acid) in styrene 25 Styrene 984 CBA-60 (6%) 218 Witco anti-separation additive

Hycar 1300X31 52 Poly (butadiene-Q-acrylonitrile) rubber; 30 improves binding

Tert-butyl- 77 Free radical initiator peroxybenzoate

Calcium stearate 206 ifol release agent

Calwhite II Calcium Carbonate Filler 35 Titanium Oxide 206 Pigment

1C C2 08 0J

- 11 - LP-90 288 Polyvinyl Acetate; low molecular weight P-710 140 polypropylene oxide; "low-profile" additive 5 Vinyl toluene 45 "Low-profile" additive

Zinc stearate 46 Thickener

Marinco H 185 Magnesium hydroxide thickener

The resin was made up to SMC and allowed to mature for several days. Typical viscosity of the resin at the time of molding was 6-20 MM cps (6000-20,000 Pa.s) vs. typically 20-40 MM cps (20,000-40,000 Pa.s).

The SMC was formed at 30-40 tons (27.2-36.3 metric 15 tons) (instead of standard 108 tons [98 metric tons]), and a good surface protruding part was obtained from a 12 x 18 (305 mm x 457 mm) shape.

Surface analysis yielded a Loria value of 36.

A very acceptable Loria value for auto parts is a 20 Loria value of 50-70 (lower values mean a smoother surface).

Example III

BBRSTB STEP

To a 10-gallon, 316 stainless steel reactor, the following is added: Ingredient Quantity

Maleine anhydride 18.51 kg

Propylene glycol 15.79 kg

Toluhydroquinone 14.0 g 30 Heat the reactants to 205 ° C and bring them to the following end point:

Acid value = 40-45 mg KOH / g resin Melt viscosity (cone & plate) - 3.9-4.5 poise (0.39-0.45 Pa.s) r! v. . > - 12 -

Cool the reaction to 135 ° C and add the following:

TWBBDB STEP

ingredient Quantity

Toluhydroquinone 1.50 g 5 Dibutyltin oxide 10.0 g

Propoxylated allyl alcohol 2.0 kg Heat again to 200 ° C and continue to the following end points:

Acid value = 18-22 10 Melt viscosity = 6-7 poise (0.6-0.7 Pa.s)

Dilute

The above described resin is lowered into styrene heated to 80 ° C:

Ingredient Quantity 15 Styrene 15.0 kg p-Benzoquinone 0.71 g

Hydroquinone 3.55 g

Example IV

BBRSTB STEP

20 The following is added to a 10-gallon, 316 stainless steel reactor: Ingredient Quantity

Propylene glycol 16.68 kg

Maleic anhydride 18.59 kg. Benzoic acid 2.51 kg

Toluhydroquinone 7.5 g

Heat the reactant to 205 ° C and bring to the following end points:

Acid value = 2025 mg KOH / g resin 30 Melt viscosity (cone & plate) = 7.5-9.0 poise (0.75-0.90 Pa.s) - 13 -

Dilute

The above-mentioned resin is lowered into styrene heated to 80 ° C

Ingredient Quantity 5 Styrene 13.2 kg p-Benzoquinone 0.63 g

Hydroquinone 3.0 g

1C

Claims (20)

An unsaturated low molecular weight polyester resin sheet forming composition comprising: a low molecular weight unsaturated polyester comprising a polycondensation product of one or more polyhydric alcohols and one or more ethylenically unsaturated polycarboxylic acids; and non-reactive or reactive end groups in which the reactive end groups are able to react with the unsaturated polyester and are able to react with an alkylenically unsaturated monomer if present and also capable of blocking the polyester chain end from complexation with thickeners during the ripening process leading to low pressure forming compounds, and in which the non-reactive end groups are unable to react with the unsaturated polyester or the alkylenically unsaturated monomer if it is present, but are capable of the polyester chain end to block for complexing with thickeners during the maturation process to form low pressure forming compounds. The composition of claim 1 wherein the unsaturated end groups are glycidyl acrylates represented by the formula: O R 1 R 2 -O-C-C = CH 2 wherein R x is hydrogen or an alkyl radical of 1 to 5 carbon atoms, and R 2 is a glycidyl ester group of the formula: O CH 2 - CH - CH 2 -; or 30 O is CH2 - CH - CH2 - R3, wherein R3 ranges from C7H14O3- to CnH2oC> 3-, wherein the glycidyl acrylates terminate some of the unsaturated end groups and low molecular weight polyester. 1 u, -. - 15 - The composition of claim 2 wherein R 1 is hydrogen or an alkyl radical of 1 to 3 carbon atoms, R 2 varies from C 3 H 50 O to C 10 H 19 O 4, and R 3 ranges from C 7 H 140 3 to C 8 H 160 3. The composition of claim 2 wherein Rx is hydrogen or a methyl group, and R2 is C3H5O-. The composition of claim 2 wherein the glycidyl acrylate is glycidyl methacrylate. The composition of claim 1 wherein the 10 unsaturated end groups are dihydric alcohols represented by the formula: ho- (r4-o) x-oh wherein R4 is an alkyl radical of 2-10 carbon atoms and X is an integer from 1 to 4 . The composition of claim 6 wherein R4 is an alkyl radical of 2 to 5 carbon atoms. The composition of claim 6 wherein the dihydric alcohols are selected from a group consisting of neopentyl glycol; 1,4-cyclohexanedimethanol; 2,2,4-trimethyl-1,3-pentanediol; and 2-methyl-1,3-propanediol. The composition of claim 1 wherein the unsaturated end groups are polycarboxylic acids. 10. The composition of claim 1 wherein the low molecular weight polyester has a number average molecular weight ranging from 1000 to 4000 g / mol. The composition of claim 1 wherein the low molecular weight polyester has a number average molecular weight ranging from 1000 to 4000 g / mol. 12. The composition of claim 1 comprising: one or more alkylenically unsaturated monomers copolymerizing with the unsaturated polyester. 13. The composition of claim 1 comprising: one or more "low-profile" thermoplastic polymers that cause phase separation and porosity during a curing reaction. A low molecular weight resinous composition as a plate-forming compound comprising: 1 η Λ o λ fy * · »V. * '* * ·" - 16 - an unsaturated polyester comprising a polycondensation product propylene glycol and maleic anhydride; and glycidyl methacrylate which copolymerizes with the unsaturated polyester, in which the glycidyl acrylates terminate some of the low molecular weight unsaturated polyester with unsaturated end groups. The composition of claim 14 comprising styrene 10 that copolymerizes with the polyester. The composition of claim 14 comprising one or more "low-profile" thermoplastic polymers. The composition of claim 14 wherein the low molecular weight polyester has a number average molecular weight ranging from 500 to 5000 g / mol. The composition of claim 14 wherein the low molecular weight polyester has a number average molecular weight ranging from 1000 to 4000 g / mol. A low molecular weight resinous composition as a plate-forming compound comprising: an unsaturated polyester comprising a polycondensation product propylene glycol and maleic anhydride; and propoxylated alkyl alcohol that copolymerizes with the unsaturated polyester, wherein the alkyl alcohol terminates some of the unsaturated low molecular weight polyester with unsaturated end groups. 20. A low molecular weight resinous composition as a plate-forming compound comprising: an unsaturated polyester comprising a polycondensation product propylene glycol and maleic anhydride; and benzoic acid which copolymerizes with the unsaturated polyester, wherein the benzoic acid terminates some of the unsaturated low molecular weight polyester with unsaturated end groups.