DE1079321B - Prevention of premature gelation in polymerizable mixtures - Google Patents

Description

GERMAN

The present invention relates to the use of a new, dihydric phenol compound, namely that of 3,6-di-n-propyl-pyrocatechol as a gel preventing agent in polymerizable mixtures of (A) monomers with I ^ C = CH ₂ groups and (B ) unsaturated polyesters of α, / 5-unsaturated olefin dicarboxylic acids and dihydric alcohols.

The production of liquid, polymerizable mixtures from (A) monomers with the grouping ^ C = CH ₂ , such as styrene, and (B) unsaturated polyesters of dihydric alcohols and a, /? - unsaturated olefin dicarboxylic acids (or mixtures of these acids with saturated aliphatic or aromatic dicarboxylic acids) is already known.

A special characteristic of these mixtures is their ability to polymerize with formation thermosetting resins. Leave in the presence of peroxide catalysts customary for addition reactions they polymerize at moderate temperatures and with little or no pressure to form a hard, thermoset product. This rapid polymerization is very advantageous for the hardening stage. However, this ability does not stop at that but is also limited during the preceding monomer mixing steps and polyester and present during subsequent storage, both before and after addition of the peroxide catalyst. In these earlier stages, polymerisation is often very undesirable, because this creates the liquid mixtures that pour or spread into molds and joints etc. let or serve to impregnate fibers and fabrics, quickly in a gel-like or solid state, in which they can no longer be processed well in many cases permit.

In order to eliminate this tendency of the mixtures to gel prematurely, it has hitherto been common practice to add small amounts of so-called anti-gel agents to them. Agents that have been suggested to prevent gelling of the mixtures include phenols containing multiple hydroxyl groups, e.g. B. hydroquinone. This substance is economical to process and very effective as an inhibitor; however, it is disadvantageous for many uses in that it often discolors resin products made from the mixture to which it is added. In addition, hydroquinone often delays curing too much. Furthermore, its anti-gel properties are enhanced by the presence of some pigments, e.g. B. soot influenced. So if you use a mixture containing hydroquinone for coating or impregnating sheets and fiber layers, such pig prevention of premature gelation
with polymerizable mixtures

Applicant:

Pittsburgh Plate Glass Company,
Pittsburgh, Pa. (V. St. A.)

Representative: Dr. W. Beil, lawyer,
Frankfurt / M.-Höchst, Antoniterstr. 36

Claimed priority:
V. St. v. America April 19, 1956

Roger Morris Christenson, Gibsonia, Pa.,

Bari Bucket Parker, Allison Park, Pa.,
and Chester Lawrence Parris, Pittsburgh, Pa.

(V. St. Α.),
have been named as inventors

contain elements as a dye, then harden those lying over the pigment-containing fiber parts these adjacent layers of resin within different times than the further resin layers that above which there are no pigments or only small amounts of fiber parts containing them. In the case of structures in which the polymerization products are in contact with plates or layers formed by such Colored patterns formed by pigments can in this way cause irregularities on the surface, so-called shadow effects, corresponding to the outlines of the pattern, arise.

Also other phenols with multiple hydroxyl groups and branched hydrocarbon chains, such as tert. Butyl catechol and 3-isopropyl catechol, has already been used as anti-gel agents for said polymerizable mixtures; she However, they proved to be not entirely satisfactory in that they were also effective in their effects, e.g. B. can be influenced by soot and shadow effects can arise as soon as the resin comes into contact with soot comes.

The present invention is based on the discovery of 3,6-di-n-propyl catechol, the one represents a new connection, and furthermore on the discovery that this connection, already if use them in very small quantities to form the polymerizable

905 769/587

mix of (A) a monomer with a ^ C = CH ₂ group and (B) an unsaturated polyester of a dihydric alcohol and an α, /? ~ unsaturated olefin dicarboxylic acid is an excellent anti-gel agent. The hardening of resin mixtures of the type mentioned, which are protected against premature gelation by 3,6-di-n-propyl-pyrocatechol, is hardly affected by pigments, in particular carbon black, or at least not to the same extent as the hardening of the previously processed mixtures , which previously used as inhibitors phenolic compounds, such as hydroquinone or tert. Butyl catechol, to prevent the. Gelation included. If one uses mixtures which contain 3,6-di-n-propyl-pyrocatechol as anti-gel agent for impregnating or coating layers containing the pigments mentioned, no or at most weak shadow effects occur.

It has also been found that the polymerizable mixtures containing the new agent are unusually durable, that is, mixtures of a monomer with the grouping ^ C = CH ₂ and an unsaturated polyester of an α, / 3-unsaturated olefin dicarboxylic acid with a divalent one Alcohol even after adding the peroxide catalyst, e.g. B. of benzoyl peroxide, does not gel for a considerable time. This is advantageous insofar as it enables the preparation of larger batches of the mixtures with the addition of peroxide and the processing of the mixtures without premature and undesired solidification or gelling. If, however, such mixtures are heated to the customary curing temperatures during further processing, they cure quickly and solidify into hard masses without significant discoloration.

The 3,6-di-n-propyl catechol is produced by hydrogenation of diallyl catechol, the arises from the diallyl ether of pyrocatechol by rearrangement (see Chem. Centralblatt, 1926, Part I, P. 3144, para. 3). For this manufacturing process, no Protection claimed.

The present invention relates to the use of 3,6-di-n-propyl-pyrocatechol as anti-gel agent for polymerizable mixtures of monomers and polyesters of dihydric alcohols with α, / J-unsaturated olefin dicarboxylic acids. The monomers are usually liquid prior to curing and can serve as liquid diluents for the polyesters. They contain an I ^ C = CH _{2 group} attached to a negative radical, e.g. B. a benzene ring, a halogen atom or a carboxylic acid residue, is bonded. They are usually polymerizable per se, with homopolymers being formed, but form polymerization products even more quickly together with unsaturated polyesters. Many of these monomers and many of the polyesters are described in U.S. Patents 2,593,787 and 2,676,947.

The unsaturated polyesters in question are derived from dihydric alcohols and α, / 5-unsaturated alcohols Oleindicarboxylic acids from.

It is often advantageous to replace some of the unsaturated acid in these esters with a saturated aliphatic one or to replace aromatic dicarboxylic acid, d. H. by an acid with aliphatic hydrocarbon residues between the carboxyl groups, e.g. B. adipic acid, or by an acid that has a benzene ring contains, e.g. B. phthalic acid and its isomers. The double bonds participate in the polymerization of the benzene ring. Acids that have triple or acetylenic bonds cannot be used or have other unsaturated groups which have a different function for the second acid radical than that of carboxyl groups ..

The saturated aliphatic or aromatic dicarboxylic acids can be used in a ratio of about 0.25 up to 12 moles per 1 mole of the α, / J-unsaturated Use olefin dicarboxylic acid.

ίο Instead of the »dicarboxylic acids« you can also use the anhydrides of acids are used. Often the anhydrides are even used for the manufacture of the polyesters more suitable than the free acids from which they are derived; in each case the obtained are polyesters same.

The monomers described can be processed with the polyesters in amounts between about 10 and 50 percent by weight, based on the total mixture. The 3,6-di-n-propyl pyrocatechol can be added in a ratio of about 0.001 to 0.1 percent by weight, based on the total mixture. These mixtures are expediently prepared by first adding the anti-gel agent to the styrene or the polyester. But you can also add the 3,6-di-n-propyl-pyrocatechol to the polyester during its production in the heat. The polyester and the Styrpl can be in sufficiently warm state, so that the mixture is liquid enough for further processing, mixing, vorausge ¹ -sets that included in at least one of the constituents of the 3,6-di-n-propyl-catechol is. After cooling, these mixtures can be stored for a fairly long time at ordinary temperature without the risk of premature gelation.

A polymerization catalyst is added to the stabilized mixtures for curing, preferably a peroxide catalyst, e.g. B. benzoyl peroxide, tert. Butyl hydroperoxide, cyclohexyl hydroperoxide, Acetyl peroxide, lauroyl peroxide or the like.

These catalysts are used in amounts between about 0.01 and about 5 percent by weight, based on weight on the mixture.

The following example explains the use of 3,6-di-n-propyl pyrocatechol as an agent to prevent gelation in a polymerizable mixture of a monomer with a ^ C = CH _{2 group} and an unsaturated polyester of a, /? - unsaturated olefin dicarboxylic acid.

example 1

The polyester was made from the following raw materials:

Maleic acid 9 moles

Phthalic acid 11 moles

Propylene glycol 22 moles

It was mixed with a monomer (styrene) and an anti-gel agent according to the following recipe:

Parts by weight

Polyester 600

Styrene 250

Anti-gel agent 0.09

In each case, the anti-gel agent was added to the styrene prior to its blending with the polyester added.

For comparison purposes, a series of samples were then prepared, each of which is the above

Composition exhibited. One of the samples was stabilized with hydroquinone, a second with tert. Butyl catechol and a third with 3,6-di-n-propyl catechol. The styrene that the anti-gel agent is used for was added, was added to the polyester, which was in the liquid state and about 120 ° C was warm.

All three samples were tested using the L.P.E. method (L.P.E. = liquid peak exotherm; analogously: Heat dissipation of the liquid sample during hardening until the temperature maximum is reached). This was carried out by adding 1 percent by weight benzoyl peroxide to the samples, a portion of each sample in poured a test tube about 16 mm in diameter with a thermocouple in the middle and that Glass placed in a 82 ° C water bath. The time, in minutes, it took the sample to move from 65 ° C Reaching the highest temperature reached was assumed to be the L. P.E. value. she is a Indicator for the hardening speed of the sample. This test was carried out with both freshly prepared Samples, as well as those carried out with those that had already been stored for 24 hours.

The shelf life of the samples in storage containers was determined by catalyzing a sample of the The mixture was stored at 38 ° C. until gelling began. This time is a measure of that Shelf life.

This is followed by a table with the results of the tests:

Anti-gel agents
(0.09 g each) Hydroquinone tert. Butyl fiery
catechin 3,6-di-n-propyl-
catechol LPE value (fresh sample) ............
LPE value (after 24 hours)
Shelf life (hours) 5.9
7.1
20th 5.1
5.4
7 to 11 6.5
6.2
22nd

At the hardening temperatures, the specimens rapidly solidify to form hot-hardened, light-colored castings that are Allow to harden further by heating to about 120 ° C. From the table above it can be seen that the Shelf life of those samples containing 3,6-di-n-propylpyrocatechol contains is larger than that of other samples. On the other hand is the curing speed very good. The most important fact to be noted, however, is that the L.P.E. value of the mixture with The 3,6-di-n-propyl catechol additive was somewhat shorter than the fresh one after storage for 24 hours produced samples is, in contrast to the other samples, in which all L.P.E. values on storage increased. This tendency of 3,6-di-n-propylpyrocatechol to lower the L.P.E. value is of importance when using the mixtures prepared with them for coating or other treatments wants to use surfaces that affect the curing properties of the resin Contain pigments such as carbon black. It has been shown that if the mixtures contain such anti-gelling agents, like hydroquinone or tert. Butyl catechol, with which the L.P.E. values during storage increase, serious difficulties then arise due to irregular influences on the surfaces If such mixtures are brought into contact with color samples, such pigments can be used for their printing containing colors can be used. In contrast, the mixtures contain 3,6-di-n-propyl pyrocatechol as an anti-gel agent, these difficulties do not occur at all or only to a minor extent.

The 3,6-di-n-propyl catechol serves as a good anti-gel agent during storage of the Mixture, especially before adding the catalyst. Such mixtures can take weeks or even Store for months without risk. After adding the catalyst, the mixtures can be left at about 75 to 250.degree solidify rapidly to form heat-hardened masses. The mixtures are for coating or impregnating Paper, fiberglass asbestos, cotton or other materials can also be used for the production of Castings and other structures.

The samples described in the following example allow a simple one that is perceptible to the eye Comparison showing the superior surface uniformity of a paper layer shows the coating films of polymerizable mixtures that are used as anti-gel agents, 3,6-din-propyl-pyrocatechol included if a pattern with a soot-containing color is printed on the paper.

Example II

In this example, the 3,6-di-n-propyl catechol is compared to hydroquinone, one at such mixtures as usual anti-gelling agents as well as with 3-isopropyl-pyrocatechol. The latter Compound is most common inhibitors, e.g. B. hydroquinone and tert. Butyl catechol, substantially superior. The comparison of 3,6-di-n-propyl-pyrocatechol with the latter So means is a rigorous test.

In these experiments, the backing layer consisted of sheets of porous, absorbent paper that were attached to each other were connected. The top layer consisted of a thin, tough sheet of proportion opaque paper with alternating black and white stripes. The black ones Stripes had been printed with a soot-containing ink.

In this experiment, the printed sheet was first covered with the liquid polyester-monomer mixture for a while impregnated, then placed on the base made of porous paper and then again with a layer of the polyester-monomer mixture coated in which the anti-gel agent used for comparison was dissolved.

Sample 1: The polyester for this example was derived from propylene glycol made with a blend was esterified from equal molar amounts of maleic anhydride and phthalic anhydride. The polymerizable Mixture consisted of:

Weight percent

Polyester 75

Styrene 25

Hydroquinone 0.03 (based on the

Polyester component)

Benzoyl peroxide .... 1 (based on the

Mixture)

Sample 2: In this sample, the polyester component was a polypropylene glycol ester of a mixture of 9 moles of maleic anhydride and 11 moles

Claims (1)

7 8 Phthalic anhydride. From this polyester those samples that contain the hydroquinone or the 3-iso- contained a polymerizable mixture according to the following propyl pyrocatechol, clearly unequal zept produced: moderate, which is already externally through depressions Weight percent ^at those points of the paper showed which with Pol ester 70 ⁵ ^ ^he were covered in black paint while over Stvfol "So ^ ^{en we} ^ ^en places the paper the plastic layer 3 Isooroovi br'en'z was somewhat sublime. These are irregularities "catechin" ...... ".... 0.015 (based on that ^for technical products mostly very undesirable. Polyester) Benzoyl peroxide 1 (based on claim ^10: Use of 3,6-di-n-propyl catechol Sample 3: In this sample, the impregnation to prevent premature gelation was mixture the same as in sample 2, only the polymerizable mixture was made of a mono- 3-isopropyl catechol by an equal amount of 15 mers with a ^ C = CH _{2 group} and 3,6-Di-n-propyl-pyrocatechol replaced. an unsaturated polyester made of a two- For hardening, the samples were immersed in a calorific alcohol, a ^ -unsaturated olefin chamber and 15 minutes at 95 ° C dicarboxylic acid and optionally a saturated one warms. The samples were all well cured. The dicarboxylic acid. Surfaces of those samples which are used as gelling 20 Contraceptive 3,6-di-n-propyl-pyrocatechol - Publications considered: held, proved to be smooth French patent specification No. 1 090 244; and evenly; whereas the surfaces were U.S. Patent No. 2,643,985. © 909 769/58? 3.60