NO743553L - - Google Patents

Description

Diallyl esters of dicarboxylic acids

This invention relates to diallyl esters of dicarboxylic acids and especially diallyl esters of aliphatic dicarboxylic acids and their use as crosslinking co-reactants for fluorocarbon polymers.

It is known that high temperature resistant fluorocarbon polymers

have a combination of mechanical, dielectric and chemical properties that make them particularly suitable as electrical insulation materials.

However, in order to utilize these fluorocarbon polymers maximally under high temperature or overload conditions, it is necessary to crosslink the polymers to further increase their strength and resistance to deformation.

s'j on.

Cross-linking of high-temperature-resistant fluorocarbon polymers has always been a problem since the polymers are normally processed at relatively high temperatures, and chemical cross-linking agents that are effective under such conditions are very limited. For example, it is not possible to process fluorocarbon polymers such as ethylene tetrafluoroethylene or ethylene chlorotrifluoroethylene copolymers in the molten state prior to cross-linking using known chemical cross-linking agents and techniques since the chemical cross-linking systems react too early during the processing of the melt at the high temperature necessary to extrude them polymers. As a result of this premature reaction, these crosslinking agents are not available to effect crosslinking of the extruded products and thus effective crosslinking cannot be achieved. As an alternative to chemical crosslinking, irradiation crosslinking of these polymers has been studied. Although some cross-linking of these polymers can be achieved by exposing them to relatively high doses of irradiation, the resulting cross-linked products are not commercially acceptable due to cost and general product characteristics. Therefore, it would be highly desirable and commercially important to produce suitable crosslinking coreactants for use with fluorocarbon polymers that would allow crosslinking of these polymers at moderate irradiation doses after processing at high temperature as found in extrusion and certain molding techniques.

We have now found a new class of cross-linking agents which are stable throughout all processing processes of the forge and which easily form homogeneous cross-linked systems upon irradiation. Processing temperatures even above 370°C can be used without significant or detrimental thermal reaction or vaporization occurring during a melt processing such as extrusion prior to the radiation activated crosslinking.

The crosslinking coreactants used in this invention are

generally diallyl esters of dicarboxylic acids which correspond to the following structural formula:

where R is an organic radical containing from 4-20 carbon atoms and is selected from the group consisting of alkyl radicals, cycloalkyl radicals, mixed alkylcycloalkyl radicals and aralkyl radicals, R' and R" are independently selected from hydrogen, alkyl, cycloalkyl, aralkyl and aryl radicals and the total number of carbon atoms in R, R' and R" is from 10-34.

In formula I, preferably, but not necessarily, the carbonyl carbon in the alkyloxycarbonyl group is attached to an alkyl carbon. When R in formula I is an aralkyl, or when R' and R" are aryl or aralkyl radicals,

moreover, the ratio between aromatic carbons and aliphatic (or alicyclic) carbons in R, R' and R" is preferably less than about 3:1,

and preferably less than approx. 2:1.

These compounds have a combination of desirable properties

which in a special position makes them applicable for use as crosslinking coreactants for fluorocarbon polymers. Their volatility is sufficiently low and their stability sufficiently high to avoid problems during high temperature processing and molding of the polymers. The

have been found to exhibit a surprisingly effective and desirable softening effect in the polymers during processing. This allows lower processing temperatures to be used and generally facilitates extrusion and pressing of the polymers. The cross-linking agents allow irradiation by

relatively low irradiation levels and result in cross-linked materials with particularly good electrical and mechanical properties, especially against- ; resistance to deformation at high temperatures.

Examples of particularly suitable materials within the scope of invention; nelsen are the diallyl esters of dodecanoic acid and brassylic acid (1,13-tridecanedioic acid). In the latter esters, R is a single aliphatic chain containing 10 and 11 carbon atoms, respectively, and R' and R" are hydrogen atoms in Formula I above. Other examples of preferred diallyl esters for use in this invention are those prepared from bis(bicyclohexanecarboxylic acid ) where R is a bicycloalkyl radical

which contains 12 carbon atoms. Esters of "Dimeric acids" are also applicable. These are acids that are produced by acid-catalyzed dimerization of natural fatty acids with 18 carbon atoms. In these compounds, R mostly has a carbon-carbon double bond and an alicyclic ring in the remaining aliphatic chain. The acid has

the following generalized structural formula:

and an ester prepared with the acid of Formula II would correspond to the structure of Formula I where R is:

and the sum of a, b, c and d is an integer from 4 to 28.

Other examples of compounds suitable for use in

this invention is the diallyl esters of hexadecanedioic acid; octadecandlic acid; diundecylenic acid; tricyclodecanedicarboxylic acid; p-menthanedicarboxylic acid; 1,2-dicyclohexylethane-4,4<1->dicarboxylic acid; 2, 2, 3, 2', 2', 3<1->hexamethyldicyclopentyl-3,3'-dicarboxylic acid; 1,2,2-trimethylcyclopentanecarboxyl-3-B-propionic acid; methyl homocamphoric acid; β-Ethylhomocamphoric acid; 2,6-dibutylpimelic acid; α-n-octylsebacic acid; 3-Raethyl-ct-allyladipic acid; 2,2,5,5-tetramethylhexene-3-dicarboxylic acid; 3,4-diisopropylhexene-3-a , w"dicarboxylic acid; ot, a, a', ot * rtetramethyl-3, 3'-diphenyladipic acid; 2, 2, 3-trimethyl-3-carboxycyclopentylphenyl-acetic acid; 2,6- dibenzylpimelic acid; 1,3-diphenylcyclobutane-bis (a-phenylpropionic acid); 1,4, 1', 4'-tetramethyl-5, 8, 5', 8'-tetrahydr-dinaphthyl-2, 2<1->dipropionic acid and the like.

We have found that these compounds have excellent properties

as plasticizers and as cross-linking agents for fluorocarbon polymers that are processed at high temperature, including homopolymers and copolymers such as ethylene tetrafluoroethylene copolymers, ethylene chlorotrifluoroethylene copolymers, polyvinylidene fluoride homopolymers, tetrafluoroethylene vinylidene fluoride copolymers, tetrafluoroethylene hexafluoropropylene copolymers, vinylidene fluoride hexafluoropropylene copolymers, vinylidene fluoride hexafluoropropylene tetrafluoroethylene copolymers and the like. The cross-linking agent must normally be added to the fluorocarbon polymer in amounts of approx. 0.5 to 20 parts by weight per 100 parts by weight polymer.

In general, the cross-linking agents of the invention can be prepared by reaction between a suitable dicarboxylic acid with an excess of thionyl chloride, after which the acid chloride reaction product is reacted with an excess of allyl alcohol. The compounds used

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for the preparation of the dicarboxylic acids are known previously and are either commercially available or synthesis is described in the literature.

The following examples illustrate the preparation of diallyl esters useful in this invention. i Example 1: i This example illustrates the preparation of diallyl brassylate (diallyl ester of 1,13-tridecanedioic acid), a linear saturated alkyl diallyl ester.

300 grams (1.23 moles) of commercially available brassylic acid and <!>270 ml. (442 gr., 3.72 mol) thionyl chloride was refluxed for 8 hours and excess thionyl chloride distilled off under atmospheric pressure and then with a water pump vacuum. Diacyl chloride and 225 ml. (192 gr., 3.31 mol) allyl alcohol was then refluxed for 4 hours and the

the liquid mass was poured into water. After washing with water, dilute aqueous solution of sodium carbonate and again with water, the distillate boiling at 180°C/1 mm was collected. The yield was 160 gr.

medium straw colored liquid representing 40%.

Example II:

This example illustrates the preparation of a mixed unsaturated alkylcycloalkyl diallyl ester, i.e. the diallyl ester of a "Dimeric acid".

500 gr. (0.885 mole) of a dimerized fatty acid (Emery Industries "Empol 1010", with an average of 35 carbon atoms for a molecular weight of 565) and 264 gr. (2.5 mol) of thionyl chloride was refluxed overnight and the excess thionyl chloride distilled off at atmospheric pressure and then by water pump vacuum. After adding 129 gr. (2.5 mol) of allyl alcohol to the diacyl chloride, the mixture was again refluxed for 6 hours and poured into water. Washing with dilute aqueous solution of sodium carbonate and water was followed by vacuum distillation at 166°C/ 0.8 Torr. The 110 gr. which was collected represents 15.5% yield of diesters.

Example III:

This example illustrates the preparation of an alicyclic saturated diallyl ester, the diallyl ester of bis(bicyclohexanecarboxylic acid).

The dimethyl ester of diphenic acid was reduced catalytically, the ester hydrolyzed and isolated bis(bicyclohexanecarboxylic acid) was heated to obtain the stable isomer melting at 353-355°C according to the method described in U.S. Pat. Patent 3.3 25,538.

Forty grams (0.157 mol) of bis(bicyclohexanecarboxylic acid) and 56 gr.

(0.47 mol) of thionyl chloride was gently heated over a heating mantle overnight and refluxed an additional 4 hours. The excess thionyl chloride was distilled off at atmospheric pressure and then by water pump vacuum. 55 grams (0.47 mol) of allyl alcohol was added dropwise to the mixture over a 3 hour period where the reaction temperature was kept below 80°C. The solution was then refluxed for a further 3 hours, washed successively with water, dilute sodium carbonate and water. A 36 gram fraction collected at 173-176°C/1.55 mm represents a 62% yield of diallyl ester relative to the diacid.

Example IV:

This example illustrates the preparation of a branched aliphatic diallyl ester, the diallyl ester of 2,6-dibutylpimelic acid.

Ethyl n-butyl malonate prepared according to the procedure of Adams and Kamm in Organic Syntheses, Collective Volume I, pages 250-1, Second Edition 1967, John Wiley and Sons, Inc. The isolated ethyl n-butyl malonate was then alkylated with trimethylene bromide and Leonard and Robinson's procedure was carried out through the hydrolysis and decarboxylation of the dibasic acid (J. Am. Chem. Soc. 7-5, 2143 (1953). The acid was dissolved in aqueous potassium hydroxide, precipitated with hydrochloric acid, triturated with water and filtered and oven dried It melted at 106-107.5°C (Hall, Mahboob and Turner, J. Chem. Soc. 19 50, 1842 report a melting point of 107-108°C).

Then they let 54.5 gr. (0.2 mol) 2,6-dibutylpimelic acid react with 60 gr. (0.5 mole) of thionyl chloride and reflux for 8 hours. Excess thionyl chloride was distilled off under atmospheric pressure and then water pump vacuum. To the diacyl chloride in 200 ml. 31.9 gr of benzene was added. (0.55 mole) of allyl alcohol dropwise under reflux and heating continued for another hour. The cooled solution was washed with aqueous solution of sodium carbonate and water and dried over sodium sulfate. Removal of the solvent at atmospheric pressure and finally distillation under vacuum/ga 52.8 gr. (75%

of the theoretical) product boiling at 176-178°C/0.7 mm.

Example V:

This example illustrates the preparation of a mixed alkyl-aryl diallyl ester, the diallyl ester of 2,6-dibenzylpimelic acid.

The starting compound for the diacid was obtained by the same two-step alkylation procedure described in Example IV using.

of benzyl bromide instead of butyl bromide in the first step. A small sample recrystallized from cyclohexane melted at 134-136°C (cf. 137°C reported by Leonard and Robinson, J. Am. Chem. Soc. 75/2143 (1953).

Then 34.0 gr. 0.1 mol) 2,6-dibenzylpimelic acid first react with 30 gr. (0.25 mole) of thionyl chloride and then in 100 ml. benzene with 17.5 gr. (0.3 mol) allyl alcohol under the same conditions as described in example 4. The product fraction of 34.5 gr. (82% of the theoretical diester) was collected at 184-186°C/0.6 mm.

The compounds of this invention have many particularly desirable properties for high temperature processing of fluorocarbon resins. Testing by thermal analysis has shown that these compounds have excellent thermal stability and low volatility and can therefore withstand the relatively high temperature involved in press forming, extrusion and other processing of the polymers. In addition, they act as softeners in the fluorocarbons. Previously reported data indicate that many of the fluorocarbon resins have a high resistance to dissolution and swelling. The following table shows the reduction in torque obtained by adding the diallyl ester of brasyl acid to an ethylene tetrafluoroethylene copolymer. Comparisons are given showing equivalent torque readings for no addition and for a known cross-linking agent, triallyl cyanurate. 1. The torque reading was taken in a "Brabender" sigma type mixer filled with 70 gr. in each case and with the noted temperature at a cutting speed of 80 revolutions per minute..

2. Triallyl cyanurate.

3. Diallyl brassylate.

Table I indicates that triallyl cyanurate, the only cross-linking agent now used commercially with a polymer processed at high temperature, is an antiplasticizer, the torque values are higher than the blank. The lower torque values with the diallyl ester in the invention make it possible to extrude clear and homogeneous fluoro-carbon copolymers and allow marked reductions in the extrusion temperatures. With triallyl cyanurate, no good extrudates have been obtained so far.

Example VI;

Sample compositions were prepared by mixing an ethylene tetrafluoroethylene copolymer powder with 3 weight percent liquid diallyl brassylate prepared as described in Example I. MgO, 1 weight percent was added to the mixture. The blends were then compression molded at 510-520°F and subjected to irradiation at a 20 megarad dose under a 1.5 MEV electron beam accelerator to produce a cross-linked compound having the following mechanical properties at 250°C:

* Modulus in heat testing indicates the percentage elongation of a sample strip of crosslinked polymer after heating the polymer composition to 275°C, when the crosslinked material is subjected to 50 psi of stress while at this high temperature and then cooled to room temperature.

t

Example VII:

Samples of the composition in Example VI were irradiated with 20 megarads and aged at 200°C. They were then tested with regard to tensile strength and elongation after cooling to room temperature, approx. 25°C.

in

The results were as follows:

Example VIII:

This example and the following demonstrate the excellent mechanical and aging properties of the cross-linked ethylene chlorotrifluoroethylene compositions of this invention.

A polymer blend was prepared by mixing an ethylene chlorotrifluoroethylene copolymer with 6% by weight diallyl brassylate.

The blend was then compression molded at 490°F and subjected to 10 megarads of irradiation under a 1.5 MEV electron beam accelerator to produce a crosslinked polymer composition having the following mechanical properties at 250°C (above the melting point of the uncrosslinked polymer):

Example IX:

Samples of the irradiation crosslinked compositions in Example VIII were aged at 200°C and tested for tensile strength and elongation after cooling to room temperature (about 25°C). The results of these tests demonstrating the excellent aging properties of polymer blends containing diallyl brassylate cross-linking coreactant were as follows:

Example X;

Ethylenetetrafluoroethylene copolymer powder (200 gr.) was mixed with 10 gr. liquid diallyl brassylate in a Henschel Mixer and the mixed material was run through a Brabender extruder at a linear 460°F profile to obtain a rod which was then granulated. The pellets were then tube extruded into 0.115" wall thickness on a 0.036" diameter conductor, consisting of 19 strands of tinned copper in a 1" Davis extruder with a temperature profile of 530, 570 and 620°F along the cylinder, head and die respectively. The insulated conductor was then irradiated to an absorbed dose of 10 megarad under 1.5 MEV electron beam accelerator and then heated for 20 minutes at 200°C.

The insulation had a tensile strength of 6136 psi, yield strength of 4464 psi and elongation of 150%, all at a draw rate of 20" per minute. In a vertical fire test, the wire was self-extinguishing with no burn-in time. Adjacent turns on a mandrel at 200°C for 6 hours set not together. Insulation resistance was greater than 500,000 Mohm per 1000 ft. No stretching or electrical breakdown was found after a "lifetime test" where a 2 ft length was hung over a 0.75" mandrel with 0.75 pound weights at 200°C for 168 hours. Bend and impact tests were also satisfactory for a 1 foot length with a 1 pound weight that was repeatedly wound on and off over a 0.7 5" mandrel at 2 revolutions per minute in a freezer maintained at -65°F for four hours.

Example XI:

To illustrate the preparation of yet another polymer composition

which can be used in accordance with this invention, ethylene chlorotrifluoroethylene powder was mixed with five percent by weight of the diallyl ester of 2,6-dibutylpimelic acid prepared in accordance with the procedure of Example IV. The blend was compression molded at 490°F and irradiated to a 10 megarad dose under a 1.5 MEV electron beam accelerator to produce a crosslinked polymer material having the following mechanical properties:

Example XII:

In accordance with the procedure in Ex. XI, a polymer composition was prepared by powder mixing of 5% by weight diallyl ester of 2,6-dibenzylpimelic acid from example V with ethylene chlorotrifluoroethylene copolymer. The mixture was then compression molded at 490°F and irradiated to a 10 megarad dose under a 1.5 MEV electron beam accelerator to produce a cross-linked polymer material having the following mechanical properties:

Example XIII:

A powder mixture of 5% by weight diallyl ester of bis(bicyclohexylcarboxylic acid) and an ethylenetetrafluoroethylene copolymer was prepared. The mixture was then compression molded at 510°F and irradiated under a 1.5 MEV electron beam accelerator to a dose of 10 megarads. The following properties were obtained for the resulting cross-linked polymer material:

v.

It is obvious that many modifications and variations of the invention as described above can be made without deviating from the spirit and scope of the invention. The restrictions that can be applied must therefore only be those given in the attached requirements.

Claims (16)

1. A compound having the structural formula: where R is an organic radical containing from 4-20 carbon atoms and selected from the group consisting of alkyl radicals, cycloalkyl radicals, mixed alkylcycloalkyl radicals and aralkyl radicals; R' and R" are independently selected from hydrogen, alkyl, cycloalkyl, aralkyl and aryl radicals and mixtures thereof; and the total number of carbon atoms in R, R<1> and R" is from 10-34. 2. Diallyl ester of dodecanoic acid. 3. Diallyl ester of brassylic acid (1,13-tridecanedioic acid). 4. Diallyl ester of bis(bicyclohexanecarboxylic acid) 5. Diallyl esters of dimer acids. 6. A polymer composition to which is added a cross-link coreactant compound consisting of a diallyl ester having the structural formula: where R is an organic radical which "contains from 4-20 carbon atoms and is selected from the group consisting of alkyl radicals, cycloalkyl radicals, mixed alkylcycloalkyl radicals and aralkyl radicals! R' and R" are independently selected from hydrogen, alkyl, cycloalkyl, aralkyl and aryl radicals and mixtures thereof; and the total number of carbon atoms in R, R' and R" is from 10-34. 7. The polymer composition in claim 6, wherein the cross-link coreactant compound is selected from the group consisting of the diallyl esters of dodecanoic acid, brassylic acid, bis(bicyclohexanecarboxylic acid), dimer acids, hexadecanedioic acid; octadecanedioic acid; diundecylenic acid; tricyclodecanedicarboxylic acid; p-menthanedicarboxylic acid; 1,2-dicyclohexylethane-4,4'-dicarboxylic acid; 2, 2, 3, 2', 2', 3'-hexamethyldicyclopentyl-3,3'-dicarboxylic acid; 1,2,2-trimethylcyclopentanecarboxyl-3-propionic acid; methyl homocamphoric acid; 8-ethyl homocamphoric acid; 2,6-dibutylpimelic acid; α-n-octylsebacic acid; 3-methyl-allyladipic acid; 2,2,5,5,-tetramethylhexene-3-dicarboxylic acid; 3,4-diisopropylhexene-3-α-dicarboxylic acid; α, α, α', α 1-tetramethyl-8, 3'-diphenyladipic acid; 2,2,3-trimethyl-3-carboxycyclopentylphenylacetic acid; 2,6-dibenzylpimelic acid; 1,3-diphenylcyclobutane bis(α-phenylpropionic acid); 1, 4, 1<1>, 4'-tetramethyl-5, 8, 5', 8'-tetrahydrodinaphthyl-2-2'-dipropionic acid and mixtures thereof. 8. The polymer composition in claim 6, wherein said composition contains a fluorocarbon homopolymer or copolymer which must be processed at a high temperature. 9. The polymer composition in claim 8, wherein said fluorocarbon homopolymer or copolymer is selected from the group consisting of ethylene-tetrafluoroethylene copolymers, ethylene chlorotrifluoroethylene copolymers, polyvinylidene fluoride homopolymers, tetrafluoroethylenevinylidene fluoride copolymers, tetrafluoroethylenehexafluoropropylene copolymers, vinylidene fluoride hexafluoropropylene copolymers, vinylidene fluoride hexafluoropropylenetetrafluoroethylene copolymers and mixtures thereof. 10. A cross-linked polymer composition containing a diallyl ester having the structural formula: where R is an organic radical containing from 4-20 carbon atoms and is selected from the group consisting of alkyl radicals, cycloalkyl radicals, mixed alkylcycloalkyl radicals and aralkyl radicals, R' and R" are independently selected from hydrogen, alkyl-, cycloalkyl-, aralkyl- and aryl radicals and mixtures thereof; and the total number of carbon atoms in R, R' and R" is from 10-34. 11. The cross-linked polymer composition in claim 10 where said diallyl ester is selected from the group consisting of diallyl esters of dodecanoic acid, brassylic acid, bis(bicyclohexanecarboxylic acid), dimer acids, hexadecanedioic acid; octadecanedioic acid; diundecylenic acid; tricyclodecanedicarboxylic acid; p-Menthanedicarboxylic acid, 1,2-dicyclohexylethane-4,4'-dicarboxylic acid; 2, 2, 3, 2', 2', 3'-hexamethyldicyclopentyl-3,3-dicarboxylic acid; 1,2,2-trimethylcyclopentanecarboxyl 3-$-propionic acid; methyl homocamphoric acid; 3-ethyl homocamphoric acid; 2,6-dibutylpimelic acid; α-n-octylsebacic acid; 3-methyl-α-allyladipic acid; 2,2,5,5-tetramethylhexene-3-dicarboxylic acid; 3,4-diisopropylhexene-3-α,'β-dicarboxylic acid; α,α,α',α 1-tetramethyl-3,3<1->diphenyladipic acid; 2, 2, 3-trimethyl-3-carboxycyclopentylphenylacetic acid; 2,6-dibenzylpimelic acid; 1,3-diphenylcyclobutane bis(α-phenylpropionic acid); 1, 4, 1', 4'-tetramethyl-5, 8, 5', 8'-tetrahydrodinaphthyl-2,2<1->dipropionic acid and mixtures thereof. 12. The cross-linked polymer composition in claim 10 where said composition contains a fluorocarbon homopolymer or copolymer which must be processed at a high temperature. 13. The crosslinked polymer composition in claim 12 where said fluorocarbon homopolymer or copolymer is selected from the group consisting of ethylene tetrafluoroethylene copolymer, ethylene chlorotrifluoroethylene copolymer, polyvinylidene fluoride homopolymer, tetrafluoroethylene vinylidene fluoride copolymer, tetrafluoroethylene hexafluoropropylene copolymer, vinylidene fluoride hexafluoropropylene copolymer, vinyl fluoride hexapropylene tetrafluoroethylene copolymer and mixtures thereof. 14. The cross-linked polymer composition of claim 10, formed as a coating on the surface of an electrical conductor. 15. A wire product having an extruded insulation coating, said extruded coating consisting of a fluorocarbon polymer that must be processed at high temperature and a diallyl ester having the structural formula: wherein R is an organic radical containing from 4-20 carbon atoms and is selected from the group consisting of alkyl radicals, cycloalkyl radicals, mixed alkylcycloalkyl radicals and aralkyl radicals; R' and R" are independently selected from hydrogen, alkyl, cycloalkyl, aralkyl and aryl radicals and mixtures thereof; and the total number of carbon atoms in R, R' and R" is from 10-34. 16. The wire product in claim 15 where said extruded coating is cross-linked by irradiation.