JPS6345738B2 - - Google Patents

Description

Claim 1: The fibers of the roving are uniformly impregnated in the substantial absence of excess liquid with a liquid polyepoxide containing a dispersed latent heat activated epoxy curing catalyst, said polyepoxide dispersion
A thermosetting wettability characterized by a room temperature viscosity of 2000 to 5000 centipoise and swing - a tack of about 6 or less on the Albert Incometer.
Impregnated roving.

2 The room temperature viscosity of the polyepoxide dispersion is 3000
A wet-impregnated roving according to claim 1, wherein the wet-impregnated roving is ~4000 centipoise.

3. The wet-impregnated roving of claim 1, wherein said polyepoxide dispersion comprises a liquid or semi-liquid diglycidyl ether having an epoxide equivalent weight of about 200 or less.

4. The wet-impregnated roving of claim 3, wherein said diglycidyl ether is a diglycidyl ether of bisphenol having an epoxide equivalent weight of about 175.

5 The diglycidyl ether of said bisphenols is present in an amount of 2% to 20% based on the total weight of the mixture.
A wet-impregnated roving according to claim 4, further comprising a low viscosity liquid diglycidyl ether of a polyether of _C2 - _C4 glycols.

6. Claim 5, wherein said low viscosity liquid is a diglycidyl ether of polyoxypropylene glycol having an epoxide equivalent weight of about 190.
Wet-impregnated rovings as described in Section.

7. The wet-impregnated roving of claim 1, wherein said epoxy curing catalyst comprises dicyandiamide.

8. A wet-impregnated roving according to any one of the preceding claims, wherein the wet-impregnated roving is wound around a supply package, the wet-impregnated roving being in contact with itself within the package. .

9. The fibers of the roving have an epoxide equivalent weight of about 200 or less mixed with a low viscosity liquid diglycidyl ether of a polyether of _C2 - _C7 glycols from 2% to 20% based on the total weight of the mixture. A polyepoxide dispersion that is a liquid or semi-liquid mixture of a diglycidyl ether of bisphenol and dicyandiamide, which is a heat-activated curing catalyst for the diglycidyl ether, in the substantial absence of excess liquid. is uniformly impregnated, and the polyepoxide dispersion is 2000 ~
A thermosetting wet-impregnated roving wound on a supply package characterized by having a room temperature viscosity of 5000 centipoise and in contact with the wet roving within the package.

10. The product of claim 9, wherein the low viscosity liquid is a diglycidyl ether of polyoxypropylene glycol having an epoxide equivalent weight of about 190, and the viscosity of the polyepoxide dispersion is between 3000 and 4000 centipoise. .

11 (Correction) An untwisted dry multifilament roving containing a latent heat activated epoxy curing catalyst dispersed therein and having a room temperature viscosity of 2000 to 5000 centipoise and a tack of less than about 6 on the Swing-Albert Incometer. impregnation with a liquid polyepoxide, in which the liquid is heated to an elevated temperature that is insufficient to activate the curing catalyst, and reduces its viscosity to Draw-out of the impregnated roving without spillage and wetness, which functions to allow uniform impregnation of the roving and then removes any excess impregnant that may be present. A method of manufacturing a thermosetting wet-impregnated roving that can be wrapped into a wet supply package that can

12 The room temperature viscosity of the polyepoxide dispersion is
12. The method of claim 11, wherein the irradiance is between 3000 and 4000 centipoise.

13. The method of claim 11, wherein said epoxy curing catalyst comprises dicyandiamide and said bath is maintained at a temperature of about 130°C.

14 The polyepoxide dispersion is 2% to 20%
of a bisphenol having an epoxide equivalent weight of about 175 mixed with a diglycidyl ether of a polyoxypropylene glycol having an epoxide equivalent weight of about 190, in which case said glycol-based polyepoxide The proportion of is based on the total weight of the polyepoxide dispersion.
12. The method according to any one of paragraphs 12 and 13.

15. The method of claim 11, wherein the wet-impregnated roving is twisted after being impregnated and then wound into a supply package.

TECHNICAL FIELD The present invention relates to a thermosetting wet-impregnated roving useful in the production of fiber composite materials, particularly a wet-impregnated roving that is formed into a package and stored with a liquid resin, but which can be removed from the package for use without damage. Regarding roving.

BACKGROUND OF THE INVENTION The production of fiber composite materials using thermosetting impregnated rovings is well known and important because fiber composite materials are lightweight, strong, and can be used to form products of various shapes. It's becoming more sexual. The manufacture of large products is of particular importance. I encountered all kinds of problems.

The most straightforward solution is to use dry rovings and impregnate them with liquid resin during the formation of the fiber composite. However, apart from the physical difficulty of doing this, when the liquid resin is of low viscosity, the low viscosity liquid resin oozes out onto the fiber composite and into resin-rich areas. and create resin-poor areas.
Neither of them is desirable and both reduce the strength of the product. On the other hand, when the resin is sufficiently viscous to resist exudation, it will not be able to penetrate well into the interior of the filaments of the multifilament roving being impregnated, so that again the final product will be defective. . Also, while resins are usually viscous liquids, the tackiness of the resin makes it sticky to textile machinery, making it impossible to braid wet-impregnated rovings, for example. Although impregnation on the way to the fiber composite is not a primary aspect of the invention, impregnation is also improved by the invention.

The use of pre-impregnated rovings has also become important. The principal method in this direction is the use of a thermoplastic overcoat around the roving which is impregnated with a semi-solid thermoset resin. The inventors' collaborators at DeSoto, Inc. have patented U.S. Patent No. 4187357, issued February 5, 1980; Considerable progress has been made in this direction, as described in US Pat.

In these disclosures, dry impregnated rovings, which typically include a relatively expensive thermoplastic resin in a thermosetting resin impregnating agent such as a polysulfone resin, are compatible with the hot melt impregnated resin system. Overcoated with thermoplastic resin coating. Thermoplastic resins increase product cost; organic solvents are usually required and must be removed, and the impregnation and coating process is slow, which also increases product cost. While it is advantageous to have the opportunity to have suitably impregnated rovings that can be drawn from a supply of impregnated rovings as needed and handled by the textile equipment, it has limitations. Yes, and some of them received particular attention.

Wet impregnated rovings were also formed into packages as described in U.S. Pat. No. 4,147,253, issued April 3, 1979. However, the low tack impregnant used in that patent was an inherently expensive UV curable liquid. Also,
The UV-cured product was not as strong as the previously used thermoset products. Also, the liquid used in that patent was of low viscosity, so special winding techniques had to be used to prevent the liquid used from flowing through the package. Such flow is acceptable for the manufacture of composites where ultraviolet light can be used to "freeze" the resin on the forming product during the application of the wet-impregnated roving, but the thermosetting This is not very easy to do with liquids, so this limits the effectiveness of the system shown in the patent.

Although the present invention is thermosetting, it can be applied at low viscosity to ensure proper penetration of the applied liquid resin in the roving.
The aforementioned problems are overcome by the use of wet-impregnated rovings that have low tack at relatively high viscosities. It is an important feature of the present invention that this is done without the use of organic solvents.

DISCLOSURE OF THE INVENTION According to the present invention, a viscous liquid polyepoxide has a latent heat-activated epoxy curing catalyst dispersed therein, and the mixture is insufficient to activate the catalyst to reduce the viscosity. heated to an elevated temperature. This low viscosity heated mixture is applied to and impregnated into a multifilament roving, and the so impregnated roving is then used, preferably by winding into a supply package. Contact of the heated mixture with the cold filament in the roving and with air causes a rapid decrease in its temperature and increases its viscosity. As a result, the high viscosity of the cooled polyepoxide mixture prevents it from flowing when the wet-impregnated multifilament roving is rolled into a package or applied to a fiber composite product.

An important point is the discovery that mixtures of latent catalyst-containing liquid polyepoxides have low tack, which is quite different from ordinary thermosetting resin mixtures.
This low tack is unique as it allows the wet-impregnated roving to be handled with textile machinery and to be extracted from the wet supply package.

Another important point is that its high viscosity prevents the liquid mixture from flowing out, so that it is no longer necessary to use specially wound supply packages.

Although various latent catalysts can be used, dicyandiamide moderately reduces the viscosity in the absence of added organic solvents, as it resists decomposition even at sufficiently high temperatures to allow uniform impregnation of the roving. Particularly applicable. At the same time, dicyandiamide provides rapid curing at moderately elevated temperatures.

Preferred polyepoxides are liquid or semi-liquid diglycidyl ethers having an epoxide equivalent weight of about 200 or less. Diglycidyl ethers of bisphenols, such as bisphenol A, are particularly contemplated. Illustrative of these is the Dow product DER-332, which is a viscous liquid with an epoxide equivalent weight of about 175 and an average molecular weight of about 350. Epon 828 from Shell
(Epon828) is also effective.

A feature of the invention is the addition of a small proportion of diglycidyl ethers of polyethers of _C2 - _C4 glycols, in a small proportion of 2% to 20%, based on the total weight of the mixture, to reduce the viscosity. The polyoxyalkylene glycols used can have a molecular weight of up to about 500. Illustrative of these products is the diglycidyl ether of polyoxypropylene glycol with an epoxide equivalent weight of 190 and an average molecular weight of about 380. The Dow product DER-736 is particularly effective. It is a low viscosity liquid, minimizing the temperature required to provide a low viscosity that allows uniform impregnation without the use of volatile organic solvents. Furthermore, the low viscosity is given at elevated temperatures, and with decreasing temperature there is a significant viscosity increase, which prevents undesired runoff.

Of course, small proportions of volatile solvents may be used, but this increases cost and imposes the burden of removing the solvent prior to use or package formation, so this is a disadvantage. .

Although it is preferable that no organic solvent is present,
If added, the solvent selected must be one that volatilizes at such low temperatures that decomposition of the latent catalyst is avoided. If used, methylene chloride is exemplified as a suitable solvent, but it should be used in the lowest amount to minimize the added cost associated with its use.

Mixtures of latent catalyst-containing liquid polyepoxides were prepared using a swing-Albert incometer (Thwing
- viscosity of about 6 or less on Albertinkometer) and 2000 to 5000 centipoise at room temperature, preferably
It should have a viscosity of 3000-4000 centipoise.

Although dicyandiamide is the preferred latent heat activated epoxy curing catalyst, other catalysts within this art-recognized class include trimellitic anhydride, pyromellitic anhydride, and chlorendic anhydride. The term "catalyst" as used in this invention includes agents that release compounds that react directly with epoxy groups, such as amines released when dicyandiamide is heated.

The temperature at which the catalyst-containing liquid polyepoxide mixture can be heated to reduce its viscosity and effectively uniformly impregnate the catalyst without activating the catalyst depends on the catalyst selected. For dicyandiamide, about 130〓 can be used completely;
And although this is not a very high temperature, a rapid viscosity reduction is indeed observed, which is sufficient to allow uniform impregnation of the roving.

Although a mild temperature is sufficient to reduce viscosity, temperatures of about 250° to about 500° cause rapid curing, hardness,
Provides a fiber composite material that is strong and has good bending strength.

Impregnation can be carried out, such as by running the dry roving through a bath of heated liquid polyepoxide mixture and then squeezing out excess liquid as the wet roving exits the bath, or by passing the dry roving onto a roller coated with the liquid polyepoxide mixture. This can be done in any conventional manner, such as by running over the top.

The wet roving coming out of the bath quickly cools down,
It can be used directly for forming fiber composite materials. In a preferred implementation, the wet roving is rolled into a package. Within the package, the wet rovings are in contact with other wet rovings. A suitable package is described in U.S. Pat. No. 4,147,253, supra, in which the more viscous resin system of the present invention provides sufficient viscosity to prevent spillage of liquid resin within the package. From there, it can be wound into a simple coppice, or cylindrical thread, in the usual way. It will be seen that although the viscosity is still low enough for the resin to flow, the resin is in intimate contact with a large number of fibers, which reduces the flowability of the liquid resin. Although its limited viscosity prevents flow within the package cage, its stickiness is low enough to allow wet roving to be pulled from its tip with very little damage to the roving. .

Without the tack-viscosity relationship described in this invention, the wet roving will be damaged when pulled out of the package or when contacted by mechanical tools of the fiber processing equipment.

DETAILED DESCRIPTION OF THE INVENTION An amount of dicyandiamide to provide 0.7 equivalents of amine per equivalent of total epoxy functionality is ground and incorporated into 95 parts of Dow DER 332 using a three-roll mill to form a fine dispersion. get. A catalyst for epoxy-amine curing, namely a salt of amidazole and adipic acid, was added to a small portion of this dispersion. This salt is commercially available under the trade name ADX-85 and is added in an amount of 2% based on the weight of dicyandiamide. This salt is mixed into the dispersion using a mortar and pestle and the mixture is then ground to a North Standard grind rating of 3 on the Hegman Scale with the remainder of the dispersion. Add to.

The dispersion prepared above was mixed with 5 parts of a Dow product.
diluted with the addition of DER736 to approx.
A catalyst-contacted thermosetting liquid mixture with a viscosity of 3500 centipoise is obtained. When heated to 130°C, the viscosity decreases rapidly to give dicyandiamide a stable, low viscosity liquid.

Interestingly, this liquid mixture has a tendency to crystallize, forming a brittle solid when left at room temperature for 4 days. However, this brittle solid can be
It regains its low viscosity and regains its room temperature viscosity of about 3500 centipoise.

This 130% low viscosity fluid is used to impregnate fiberglass multi-fryment roving (250 yards/lb). The impregnation was uniform and the fiber surface was well wetted. Impregnation is accomplished by passing the dry roving over a roller that is immersed in a bath of hot liquid. Since the amount of resin on the roller is controlled to a measured thickness, there is no need to squeeze out excess liquid from the wet roving exiting the roller. The impregnated wet roving is then post-twisted (3/4 twist/inch - straight) and wound into 6 inch cots. The resin impregnating agent in the coop is viscous because the liquid on the fiber cools quickly to room temperature. Leaving it in the form of a pot for an extended period of time, especially since the liquid impregnant becomes more viscous over time, to the point that it requires melting prior to use.
No appreciable runoff is observed. 6 at 0
Satisfactory shelf life is obtained as shown by testing for 21 days at 68°C and 68°C. In this example, the resin in the pot gradually becomes more viscous and solidifies after about two weeks. However, by heating the wound tip to melt the solid resin, the liquid form and room temperature viscosity obtained above are restored. The viscosity simply increases or
Alternatively, regardless of whether the resin solidifies, it can be melted within a few days prior to curing to return to the desired room temperature viscosity.

The impregnated wet roving is easily removed from the winding cup at room temperature with the resin in a viscous liquid form which lasts for a short time after exposure to 130°C.
And because of its low tackiness, it could be handled with regular braiding machines. When applied in a form to give a fiber composite, the viscous liquid resin impregnant in the superimposed rovings flowed together into a single mass, expelling air from between the rovings, but leaving the viscous The resin mass did not flow into the uncured composite. Thus, air is forced out before the uncured composite material enters the curing oven. The above is useful in the production of large products, as you can be sure that voids have been removed before curing the product, and you know that it is often necessary to throw away the cured product when the holidays come after curing. It's advantageous.

The wet fiber composite is then cured in a conventional manner by wrapping it in a non-stick plastic cover that is placed in a curing oven. In the present invention, the low viscosity required for uniform impregnation is achieved without activating the curing dicyandiamide.
It has been found that the desired hardening can be achieved using a furnace held at 250 to 300 °C, although it can be achieved at 250 °C to 300 °C. At 300㎓, curing is fast and the finished fiber composite is hard and has good bending strength and good shear strength. These properties are measured by rolling rectangular rafters of cured product containing 32.6% resin by weight.

To produce larger batches, it is advisable to use a steel ball mill to disperse the dicyandiamide and ADX-85 into the epoxy resin. This is preferably done to give a North Standard grinding grade of about 7 on the Hegman scale.