Laminating resins having low organic emission (III)

TECHNICAL FIELD
This invention relates to resin compositions which cure as they are shaped, laminated, brushed, sprayed or otherwise more or less incrementally placed into the space where they are to form a product; such resins are broadly known as laminating resins, commonly have an unsaturated polyester resin base, are mixed with glass fiber reinforcement, and nearly always are employed in a solution of an organic monomer such as styrene. The organic monomer is intended to copolymerize with the resin but typically and notoriously tends also to volatilize in significant amounts into the workplace environment. The present invention is a composition and method which can be used in existing equipment, procedures, and workplaces, but which will emit far less monomer than the typical laminating resin and method heretofore.
BACKGROUND OF THE INVENTION
Many attempts have been made to devise laminating resins having low volatile emissions and still meet the physical specifications and other desirable properties of the end products, while remaining relatively easy to use. In Lee U.S. Pat. No. 4,465,806, for example, a more or less conventional unsaturated polyester resin is combined with, instead of the usual styrene, a reaction product of a polyepoxy compound and acrylic or methacrylic acid which may be the diacrylate of a polyglycidyl ether of bisphenol-A. These compounds are made from epoxy compounds, and the author of U.S. Pat. No. 4,465,806 requires that a significant portion of the epoxy groups be unreacted for use in their resin. Moreover, unlike the present invention, they form pendant OH groups.
Ethoxylated, difunctional, bisphenol-A has been used in the past as an ingredient in various types of resins, generally resins which include a significant diisocyanate component, as in Ford, Jr. et al U.S. Pat. No. 3,876,726.
European Patent Application 0 234 692 discloses a composition said to be useful as a molding resin, having the virtue of a low residual monomer concentration in the final product. The gist of the disclosure appears to be that dimethacrylates such as ethoxylated bisphenol-A dimethacrylate can be used as components of otherwise more or less conventional unsaturated polyester resins to reduce the amount of residual styrene monomer in contained molding processes such as cell molding, compression molding, and sheet molding. See also Reid and Rex U.S. Pat. No. 5,202,366, which includes a low-profile additive in a similar composition.
The daunting problem of volatile emissions during spray-up or other laminating procedures has until now been unsolved. Applicants' dramatic results detailed herein show that lamination can be performed with significantly reduced emissions in the workplace.
SUMMARY OF THE INVENTION
Our new laminating method employs a resin comprising three components. The first is a more or less conventional base resin comprising glycols and unsaturated dicarboxylic acids; optionally the base resin may also contain a saturated dicarboxylic acid. In polymeric form, they are typically maleic and phthalic acid residues, with optional isophthalic residues, interspersed with glycol residues. These glycols are commonly ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol, usually as mixtures, but many other glycols can be utilized; dicyclopentadiene may be included as well, as is known in the art. The second component is a diacrylate or dimethacrylate of alkoxylated bisphenol-A of the formula ##STR1## where m and n are independently numbers from 1 to about 10, R.sup.1 and R.sup.2 are independently, in each alkoxy group, hydrogen or CH.sub.3 and each R.sup.3 is also independently hydrogen or CH.sub.3. These two ingredients may be present in weight ratios of about 2.0:1 to about 0.5:1. The composition also includes about 10% to 60%, based on the total of the two above ingredients, of styrene, divinyl benzene or mixtures thereof. The above-described composition may also include from 1% to about 10% of N-vinyl pyrrolidone or 1% to about 20% cyclohexyl methacrylate or both, and/or 1% to about 30% ethylene glycol dimethacrylate, or vinyl toluene, all based on overall composition. The composition will also tolerate many other minor ingredients known to be useful in the unsaturated polyester and laminating art.
The compounds of interest, styrene and divinyl benzene, may be described as benzene ring compounds of the formula C.sub.6 H.sub.(6-x) (CH.dbd.CH.sub.2).sub.x where x is 1 or 2.

DETAILED DESCRIPTION OF THE INVENTION
While the problem at hand is to create a formulation which drastically differs from commercial standard laminating resins in terms of volatile emissions during application, the market dictates that it must be accomplished without significantly altering the widely used equipment and techniques of application. Accordingly, the following criteria are to be kept in mind at all times:
1. Reduced emission of volatile organic compounds--regulations will become more stringent with time.
2. Less potential hazard to human health and the environment--regulations will also become more stringent with time.
3. Minimal increase in cost when commercialized, and reason to believe cost will be reduced in the long run.
4. Compatibility between components of the resin system.
5. Reactivity that is similar to that of other commercial polyester resins.
6. Viscosity that is similar to that of other commercial polyester resins--100 to 400 cps.
7. Ability to wet glass and bond to other components of an assembly.
Many criteria have to be balanced, and, with thousands of chemicals to consider, analysis of the combinations and their effects is extremely difficult. One must decide on the important functions and properties, settle on a systematic but simple screening process, and try to develop a short list of prospective formulations which have a good chance of meeting all the criteria within a practical time period.
The proliferation of input variables to attain these objectives may be further appreciated by considering the more or less conventional unsaturated polyester compositions which may be used as a base. They are prepared by polycondensation of polycarboxylic acid derivatives, one of which must be an alpha, beta-ethylenically unsaturated polycarboxylic acid, and polyols. By polycarboxylic acid derivatives we mean to include polycarboxylic acids, their esters of lower alcohols, their acid chlorides and their anhydrides.
The ratio of polycarboxylic acid to polyol is usually a 1:1 molar ratio. However, in most esterification processes, a slight excess of polyol is utilized to compensate for polyol losses during esterification. Also, although dicarboxylic acids and diols are most frequently utilized and the 1:1 molar ratio is prevalent, the utilization of triols and the like requires the ratio of acid to polyol to be stated more precisely as one equivalent of acid per equivalent of polyol.
The unsaturated polyesters useful in this invention may be prepared from an acid mixture wherein the unsaturated polycarboxylic acid comprises as little as 20 mole percent of the total acids present, although it is generally preferred that the unsaturated polycarboxylic acid comprises about 30% or more of the total acid content.
Some of the unsaturated polycarboxylic acids useful in preparing unsaturated polyesters used in this invention include:
______________________________________Maleic acid Citraconic acidFumaric acid Glutaconic acidItaconic acid Chloromaleic acidMesaconic acid______________________________________
and the like, wherein the term "acid" is used to include the corresponding anhydrides where such anhydrides exist.
Some of the saturated and aromatically unsaturated polycarboxylic acids optionally useful in preparing unsaturated polyesters used in this invention include:
______________________________________Phthalic acid Isophthalic acidTetrahydrophthalic acid Hexahydrophthalic acidEndomethylene tetrahydrophthalic acid Glutaric acidTetrachlorophthalic acid Suberic acidHexachloroendomethylene Sebacic acidtetrahydrophthalic acidSuccinic acidAdipic acid______________________________________
and the like, wherein the term "acid" includes the corresponding anhydrides where such anhydrides exist.
Polyols useful in preparing polyesters for use in this invention are polyfunctional alcohols of the type conventionally utilized in polyester preparation. Such polyols include:
______________________________________Ethylene glycol 1,5 propanediolPropylene glycol Triethylene glycolButylene glycol GlycerolDiethylene glycol 1,4,6-hexanetriolTrimethylolpropane TrimethylolethaneDipropylene glycol PentaerythritolNeopentyl glycolAlkoxylated 2,2-bis(4-hydroxyphenyl)propane______________________________________
and the like. Although diols are generally preferred in the preparation of unsaturated polyesters, the more functional polyols, i.e. polyols having a functionality of three to five, are sometimes used.
In addition, dicyclopentadiene may be included and may be considered a normal part of the "base resin" as used herein.
During the development of the formulation, various monomers and monomer substitutes were screened, using a resin composition (hereafter designated "Resin A") prepared from the following ingredients:
______________________________________Base Resin* 60 parts by weight12% Cobalt (Promoter) 00.30Potassium (Co-promoter) 00.20N,N-Dimethylacetoacetamide 00.30(Accelerator)DDM-9 (Initiator) 01.50Monomer (as indicated below) 40 Parts by*Base Resin (Polymer) weight lbs/100 lbs lbs/60 lbs______________________________________Propylene Glycol 22.788 31.97 19.18Diethylene Glycol 04.937 6.93 4.16Phthalic Anhydride 32.734 45.92 27.55Maleic Anhydride 10.820 15.18 9.11 71.279 100.00 60.00______________________________________
The following "monomers" were utilized with Resin A:
______________________________________ Exo- therm Gel Time IntervalMonomer Mod L.sup.1) Viscosity .degree.F. min:sec min:sec______________________________________Styrene 0.120 low 335 4:30 4:39Vinyl 0.120 low 317 4:50 5:04TolueneDiallyl 0.000 high 119 19:27 27:43phthalateMeth-acrylatesn-butyl 0.001 low 186 40:58 5:28n-hexyl 0.001 incompa- tibleisodecyl 0.001 incompa- tiblecyclohexyl 0.001 high* 287 16:50 3:502-phenoxy- 0.001 high 196 8:45 3:29ethylallyl 0.001 low 331 18:20 3:372-hydroxy- 0.001 low 247 4:48 3:35ethyl2-hydroxy- 0.010 low 249 4:30 3:20ethyldicyclopentyl 0.001 very high 199 3:40 4:11isobornyl 0.000 incompa- tibleisophoronyl 0.010 incompa- tibleDimeth-acrylates1,6- 0.001 high 241 7:54 3:34hexanediolethylene 0.001 low 275 2:48 3:37glycol (EG)ethylene 0.005 low 274 2:52 3:50glycoldiethylene 0.001 medium >210 4:03 2:12glycoldiethylene 0.010 medium 252 5:40 3:13glycoltriethylene 0.001 medium 241 3:18 3:17glycoltetraethylene 0.001 medium 229 2:52 3:46glycolneopentyl 0.001 high 235 4:20 4:09glycolethoxylated 0.001 very high 171 8:50 7:30BPAC14 diol 0.001 incompa- tibleTri-methacrylatetrimethylol 0.001 high 228 2:28 4:25propaneMixtures30 EG di- 0.010 medium 295 1:49 3:12methacrylate/10 N-vinylpyrrolidinone30 EG di- 0.010 medium 286 3:11 3:29methacrylate/10 divinylbenzene30 vinyl 0.200 low 289 16:10 4:44toluene/10 N-vinylpyrrolidinone______________________________________ *This was considered unsatisfactory, but when ethoxylated BPA dimethacrylate was included to make a 3part mixture, viscosity was lowered. Of all the above monomers screened, only the Nvinyl pyrrolidinone, divinyl benzene, ethylene glycol dimethacrylate, styrene, cyclohexyl methacrylate, and vinyl toluene were not ruled out. The rest were eliminated from consideration because they were slow to react with polyester as shown by long gel time and/or low exotherm or they were not sufficiently compatible with polyester as shown by high viscosity or the outright failure to dissolve. .sup.1) Mod L is 25% hydroquinone in propylene glycol.
Liquid resin properties measured in the experiments reported below were gel time, (reported in the tables herein in minutes and seconds, as 13:17, for example), room temperature interval time, which is the time between gelation and the exothermic peak, room temperature exothermic peak which is the highest temperature reached in a 100 g mass of resin during the curing process, Brookfield viscosity, and Barcol hardness by ASTM D2583. For volatile emissions, we followed the Rule 1162 Standard Method for Static Volatile Emissions of the South Coast Air Quality Management District (California) which is incorporated herein by reference. This test is accepted as a predictor of volatile emissions in the workplace during spray-up lamination procedures. Its results are reported in two ways--grams per square meter of weight loss, and the time of emissions, in minutes and seconds. The latter measurement entails noting the point in time in which weight loss is no longer recorded, thus requiring that weight be monitored beyond the time noted.
The test requirements are as follows: An environment at 77.degree. C. and 50% relative humidity is maintained. If a controlled environment is not available, conditions should be reported for which measurements are made. A 200 gm pre-promoted resin is weighed out into a suitable dry and clean container. The container is covered and placed in a 25.degree. C. temperature bath. A balance is placed in a draft free enclosure. A gallon lid is cleaned with solvent and wiped dry. The diameter is measured to the nearest 0.1 cm. The gallon lid is placed on an inverted paper or plastic cup mounted on the balance pan. A bent paper clip is positioned in the center of the gallon lid. This weight (TARE WEIGHT) is recorded. The container is taken from the temperature bath and an appropriate volumetric or weight measure of catalyst is added. A timer is started at this point. The catalyst is mixed with the resin for one minute. The INITIAL WEIGHT is determined by pouring 100.0.+-.0.5 gm of catalyzed resin into the can lid and recording the weight. Next, the paper clip is used to determine when the resin has hardened sufficiently to allow the resin or lid to be lifted. The time (gel time) is recorded at this point. The resin is then allowed to harden in the can lid and every 15 minutes it is reweighed until concurrent weights agree to within 0.05 gm. This is recorded as the FINAL WEIGHT. The entire procedure should be repeated until duplicate samples agree to the nearest 5 gm/m.sup.2.
The volatile emissions per square meter are calculated as follows: ##EQU1##
The clear castings tests adopted were as follows:
1. Tensile strength--ASTM D638.
2. Tensile modulus--ASTM D638.
3. Elongation--ASTM D638.
4. Flexural strength--ASTM D790.
5. Flexural modulus--ASTM D790.
6. Heat deflection temperature--ASTM D648.
7. Water absorption at 150.degree. F.--ASTM D570 (modified).
The water absorption test was modified as follows: the temperature was set at 150.degree. F. and long term immersion was set at one week. In the data reported in Table I, Resin A is as described above in terms of weight; it is, in molar equivalents, a polyester resin composed of 1.0 mole maleic anhydride, 2.0 moles phthalic anhydride, 0.42 mole diethylene glycol and 2.71 moles propylene glycol. Sartomer CD480 is ethoxylated bisphenol-A dimethacrylate where m and n in the above formula total 10. Sartomer 348 is ethoxylated bisphenol-A dimethacrylate where m and n in the above formula are both 1. Mod L is 25% hydroquinone and 75% propylene glycol.
In Tables I and II, formulations containing both Sartomer and either styrene or divinyl benzene are seen to compare very well in terms of emissions with those not including styrene as a monomer.
From these it will be seen that the use of the alkoxylated BPA dimethacrylates have the effect of significantly reducing monomer emissions in styrene-containing laminating resins.
A volatility of 20.0 g/m.sup.2 or less, as measured by the test of Section 1162 of the Regulations of the South Coast (California) Air Quality District, was significantly achieved by applicants in the present invention. In fact, applicants' resins all measured under 10.0 g/m.sup.2.
TABLE I______________________________________RESIN A2 C2 S Z Al______________________________________Resin A 60.00 60.00 40.00 35.00 35.00Sartomer CD480 -- -- 15.00 15.00 15.00Sartomer 348 -- -- 20.00 20.00 20.00EG Dimethacrylate -- -- 25.00 10.00 20.00Vinyl Toluene -- 40.00 -- 10.00 --Cyclohexyl -- -- -- 10.00 --MethacrylateDivinyl Benzene -- -- -- -- 10.00Styrene 40.00 -- -- -- --Mod L 0.20 0.22 0.06 0.12 0.12RESINPROPERTIESGel time, min:sec 12:59 13:17 21:18 18:29 11:30interval, min:sec 5:58 6:54 4:32 4:11 3:26Exotherm peak, .degree.F. 345 324 249 276 294Viscosity, cps, 75.degree. F. 315 340 1,390 426 6241162 Emissions, G/M2 31.5 20.6E 3.6 6.1 9.7Barcol hardness45 minutes 45 42 47 44 52One hour 45 43 50 48 5324 hours 49 49 52 51 54CLEAR CASTINGPROPERTIESTensile strength, psi 9,308 7,555 8,069 9,635 8,176Ten. modulus, 10-5 psi 0.549 0.534 0.466 0.565 0.575Elongation, % 1.9 1.6 3.2 2.7 1.9Flexural strength, psi 16,008 15,317 10,475 16,889 15,780Flex modulus, 10-5 psi 0.586 0.573 0.322 0.444 0.482Heat deflect. temp, .degree.F. 144 138 169 142 147Water absorption,% at 150.degree. F.One day 0.89 0.91 1.01 1.19 1.267 days 1.89 1.89 2.12 1.65 1.76______________________________________ E This value was estimated based on the difference in results caused by using different end points for the 1162 test. A The surfaces of the test specimens were alligatored. This indicates a more severe problem than the weight gain indicates.
TABLE II__________________________________________________________________________Low VOC Laminating Resins Based on General Purpose Polyester__________________________________________________________________________PolymerResin E-4 V-3 F-4 G-3 D-4 ZA__________________________________________________________________________CompositionResin A 35.00 35.00 35.00 35.00 35.00 35.00Sartomer 480 15.00 15.00 15.00 15.00 15.00 15.00Sartomer 348 20.00 20.00 20.00 20.00 20.00 20.00EG Dimethacrylate -- -- -- -- 10.00 10.00Cyclahexyl Methacrylate -- -- 15.00 15.00 10.00 10.00Styrene 30.00 -- 15.00 -- 10.00 --Vinyl Toluene -- 30.00 -- 15.00 -- 10.00Mod L 00.10 00.20 00.05 00.17 00.00 00.0612% Cobalt 00.30 00.30 00.30 00.30 00.30 00.3016% Potassium 00.20 00.20 00.20 00.20 00.20 00.20Dimethyl Acetoacetamide 00.30 00.30 00.30 00.30 00.30 00.30Resin PropertiesGel Time, min:sec 29:20 37:36 31:47 33:52 19:45 38:15Interval, min:sec 10:35 09:49 11:25 07:07 10:15 07:37Exotherm, .degree.F. 301 273 220 244 231 277Viscosity, cps @ 75.degree. F. 360 382 1570 560 990 710Barcol45 minutes 00.0 00.0 00.0 00.0 36.0 00.0one hour 39.6 39.9 00.0 29.7 47.2 32.2two hours 43.9 46.0 41.6 45.6 47.8 47.2three hours 46.4 46.2 43.9 45.9 48.2 47.6four hours 46.7 46.9 44.3 46.0 48.6 47.824 hours 46.9 46.9 43.9 47.2 48.5 48.71162 Emissions, G/M2 9.7 1.8 4.8 3.6 3.0 2.4Emissions, min:sec 46:12 51:35 50:00 53:46 36:10 48:20Properties of a Clear CastingHDT, .degree.F. 147 138 127 138 133 138Tensile strength, psi 7,610 9,500 8,930 9,580 7,950 10,370Ten Modulus, 10-5 psi 0.442 0.501 0.452 0.485 0.454 0.540Elongation, % 2.00 2.30 2.70 2.50 2.00 2.60Flexural Strength, psi >19,220 >19,150 >17,060 18,400 14,980 19,410Flex Modulus, 10-5 psi 0.536 -- 0.509 0.662 0.545 --Water Absorption @ 150.degree. F.24 hours 1.07 0.81 1.30 1.07 1.22 1.04seven days 1.81 1.43 2.16 1.78 2.09 1.87__________________________________________________________________________Resin H-4 U-3 G-4 H-3 Controls__________________________________________________________________________CompositionResin A 35.00 35.00 35.00 35.00 60.00 60.00Sartomer 480 15.00 15.00 15.00 15.00 -- --Sartomer 348 20.00 20.00 20.00 20.00 -- --EG Dimethacrylate 15.00 15.00 15.00 15.00 -- --Cyclohexyl methacrylate 05.00 05.00 -- -- -- --Styrene 10.00 -- 15.00 -- 40.00 40.00Vinyl Toluene -- 10.00 -- 15.00 -- --Mod L 00.00 00.13 00.05 00.17 00.10 00.3012% Cobalt 00.30 00.30 00.30 00.30 00.30 00.3016% Potassium 00.20 00.20 00.20 00.20 00.20 00.20Dimethyl Acetoacetamide 00.30 00.30 00.30 00.30 00.30 00.30Resin PropertiesGel Time, min:sec 09:22 38:05 15:26 25,10 05:00 23:22Interval, min:sec 04:27 06:07 03:19 03:51 06:02 --Exotherm, .degree.F. 239 277 268 291 296 --Viscosity cps @ 75.degree. F. 910 790 1100 650 440 440Barcol45 minutes 46.1 00.0 44.5 00.0 41.9 --one hour 48.7 37.0 48.1 47.0 44.8 --two hours 49.2 48.6 50.0 50.8 45.4 --three hours 49.7 48.5 50.5 49.8 45.5 --four hours 49.6 48.5 50.6 50.3 45.9 --24 hours 50.4 48.5 50.3 50.7 46.2 --1162 Emissions, G/M2 1.2 7.3 2.4 4.2 12.7 24.2Emissions, min:sec 13:43 44:22 21:43 29:15 20:14 23:22Properties of a Clear CastingHDT, .degree.F. 143 136 147 159 144 --Tensile Strength, psi 7,410 10,120 6,160 9,140 8,040 --Ten Modulus, 10-5 psi 0.473 0.489 0.521 0.544 0.478 --Elongation, % 1.80 2.70 1.50 2.00 1.80 --Flexural Strength, psi 16,030 18,750 15,950 19,660 15,070 --Flex Modulus, 10-5 psi 0.569 -- 0.599 0.664 0.598 --Water Absorption @ 150.degree. F.24 hours 1.23 1.06 1.17 0.95 1.01 1.01seven days 2.14 1.78 2.14 1.84 2.11 2.11__________________________________________________________________________
Accordingly, our invention is a method of laminating comprising repeatedly applying to a surface a composition comprising (a) the base polyester polymer (resin) as described above and the alkoxylated bisphenol-A diacrylate or dimethacrylate in a ratio of 2:1 to 0.5:1 and (b) about 10% to about 60%, based on the total of (a) and (b), of either styrene, divinyl benzene or a combination thereof. In Tables I and II, the various "Sartomer" compositions, i.e. the ethoxylated bisphenol-A dimethacrylates, have 1 and 5 ethoxy groups on each side of the bisphenol-A; however, we may employ a single compound or compounds having any variation of combinations of ethoxy or propoxy groups from two to about 20 groups, preferably a total of 2 to 10 alkoxy groups.

Number	Name	Date
3983185	Dorfman	Sep 1976
4289684	Kallaur	Sep 1981
4465806	Lee	Aug 1984
5202366	Reid	Apr 1993

Laminating resins having low organic emission (III)

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Lubin, G. Handbook of Composites pp. 20, 29-30, Van Nostrand Reinhold Co. 1982.
Sartomer Company, West Chester, Pa. 1982; Product Bulletin: Sartomer 348 (Ethoxylated Bisphenol A Dimethacrylate).