GB2114141A

GB2114141A - Glass fibre product

Info

Publication number: GB2114141A
Application number: GB08303013A
Authority: GB
Inventors: Malcolm Combey; Richard John Dellar
Original assignee: Ciba Geigy AG
Current assignee: Novartis AG
Priority date: 1982-02-03
Filing date: 1983-02-03
Publication date: 1983-08-17
Also published as: GB8303013D0

Abstract

A glass fibre product comprising short lengths of glass fibres, bonded by applying a powdered binder polyester, which is saturated and is the reaction product of an aromatic dicarboxylic acid or anhydride and neopentyl glycol, and has a molecular weight up to 5000.

Description

SPECIFICATION Glass fibre products The present invention relates to fibrous products bonded with polyester resins, particularly glass fibres bonded with powdered polyester resins which may be in the form of a glass fibre mat, often called "chopped strand mat".

Such products may be used as a reinforcing agent for resinous compositions which may be moulded or formed into various articles and shapes and then hot or cold cured to form reinforced plastics articles such as laminates, roof sheeting, boats and glider planes. The resinous composition may be unsaturated polyester resin in combination with a cross-linking agent which may be a vinyl monomer, e.g. styrene.

In order to be effective in such applications the binder for the glass fibres should provide a good bond strength to the fibres to give good strength to the mat combined with a soft handle to facilitate manoeuvring the mat whilst preparing a composite or laminated. The binder should also have good solubility in the resin system being reinforced to ensure that the fibrous mat follows the desired contours of the product being made. It is also desirable that the binder should have a refractive index when dissolved in the resinous product which is close to that of the glass fibres, and to that of the cured resin. This gives good translucency to the final product.

Powdered polyester binders which have been used to date, all have ethylenic unsaturation in the molecule and are therefore capable of crosslinking, not only with the resinous composition being re-inforced, but also with itself. If any selfcross-linking occurs before use, the solubility of the polyester in the resin system being re-inforced is adversely affected. In order to avoid this problem, the conditions e.g. temperature under which the glass fibre mat is produced and stored must be carefully controlled.

We have now found a binder which satisfies the above requirements, and avoids the disadvantages associated with the use of unsaturated polyesters.

Accordingly, the present invention provides a glass fibre product comprising short lengths of glass fibres bonded together by a binder polyester, which is saturated and is the reaction product of one or more aromatic dicarboxylic acids or anhydrides or mixtures thereof and neopentyl glycol, and has a molecular weight up to 5000.

The glass fibres may be aligned but are preferably arranged haphazardly and are conveniently in chopped strands of lengths from 1 to 12 cm, usually from 3 to 7 cm and preferably having an average length of 5 cm at a density of from 250 to 750 grams per square metre.

The amount of binder polyester in the bonded glass fibre product may be from 1 to 20%, for example from 3 to 1 5% but preferably from 4 to 10% by weight based on the weight of the product.

The present invention further provides a method for producing a glass fibre product bonded with a polyester resin which comprises applying a powdered binder polyester, which is the reaction product of an aromatic dicarboxylic acid or an hydride or mixture thereof and neopentyl glycol, and has a molecular weight up to 5000, to short lengths of glass fibres, heating to a temperature above the melting point of the binder polyester and subsequently cooling to bind the glass fibres.

The powdered binder polyester may be applied simply by sprinkling or dusting on to the glass fibres. Alternatively the powdered binder polyester may be dispersed in a liquid such as water and applied to the glass fibres as an emulsion or suspension, for example by spraying.

One method of producing a glass fibre product of this invention comprises laying chopped strands of haphazardly arranged glass fibres on a conveyor belt, sprinkling the powdered binder polyester on the chopped strands, passing the mixture through an oven at a temperature above the melting point of the polyester for example at 1 500 to 2200, for about 1 to 5 minutes to make the binder polyester resin adhesive and then passing through cooled rollers to yield a bonded glass fibre mat.

The aromatic dicarboxylic acid or anhydride used to produce the binder polyester may be phthalic acid or anyhdride, isophthalic acid, tetrabromophthalic anhydride or tetrachlorophthalic an hydride. Preferably the acid is phthalic acid or anhydride or a mixture of one or both of these with isophthalic acid.

If desired, minor amounts of other acids and/or glycols may be present in the composition from which the polyester is prepared. Examples of acids which may be present are benzoic, succinic, adipic, azelaic, sebacic, pimelic or their anhydrides. Examples of glycols which may be present are ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycols andbutanediols. In addition, minor amounts of other matarials having more than two hydroxy groups per molecule may be present, for example, pentaerythritol.

Preferably, not more than 10% of these other acids and/or glycols should be present in the composition from which the binder polyester is prepared.

The binder polyester is saturated, an advantage of a saturated powdered polyester over an unsaturated one being that the temperature used for bonding is less critical as there is no danger of cross-linking occurring with subsequent reduction in the resin system being re-inforced.

The molecular weight of the binder polyester may conveniently be from 1000 to 4000 but is preferably from 1200 to 2500.

The melting point of the binder polyester may be from 500 to 1400 C, preferably from 600 to 1200 and especially from 650 to 1000C.

The binder polyester should be soluble in one or more components of unsaturated polyester resinous compositions which may subsequently be reinforced with the bonded glass fibre products of the present invention e.g. in vinyl monomers such as styrene. Conveniently, the binder polyester may be completely soluble at concentrations up to 75% by weight based on the vinyl monomer: as the solubility in the vinyl monomer increases, the wetting out time of the bonded glass fibre product by the unsaturated polyester resin in making reinforced products becomes quicker.

The Refractive Index of the binder polyester as a 50% solution in the vinyl monomer, such as styrene should be approximately similar to that of the glass fibre and the unsaturated polyester resin which is subsequently reinforced with the bonded glass fibre product of the present invention and is usually about 1.550-1.555 at 200C.

The binder polyester resin may be prepared by any conventional means for example, azeotropic distillation or by a fusion technique. The product is cooled and the solid polyester is then powdered, for example by grinding, so that the average particle size may be from 45 to 500 microns, preferably from 100 to 500 microns.

If desired, small amounts of other compounds may be added to the powdered binder polyester to improve its free flowing properties. Examples of such compounds are zinc stearate and calcium stearate. These other compounds may be added in amounts of from 0.1 to 5%, preferably 0.5 to 2% by weight based on the weight of binder polyester.

The invention is illustrated by the following Examples.

EXAMPLE 1 a) To a 2-litre, 4-necked flask were charged 6 moles phthalic anhydride, 6.8 moles neopentyl glycol and 50g xylene. The flask was fitted with a stirrer, a vacuum jacketed Vigreux column with Dean and Stark tube and reflux condenser, nitrogen inlet, dropping funnel and thermometers showing the temperature of the reaction mass and at the column head.

The reaction mass was heated with stirring in an atmosphere of nitrogen at 21O0C. Water of reaction was periodicaliy run off from the Dean and Stark tube, and refluxing was maintained with further small additions of xylene from the dropping funnel. When the evolution of water ceased and titration of a sample of the reaction mass showed an acid value below 2 mg KOH/g the heating was stopped.

The apparatus was then modified for distillation under water pump vacuum and the xylene was distilled off. The product was poured into trays, allowed to solidify as a pale amber vitreous mass and was ground to a fine powder, yield 1481 9.

The product had an acid value of 1.7 mg KOH/g and OH value of 54 mg KOH/g, a melting range of 67--870C and a molecular weight of 2000.

b) Preparation of glass fibre mat Haphazardly arranged chopped strands of glass fibre of average length 5 cm are placed on a conveyor belt at a density of 500 grams per square metre. The powdered polyester prepared above and containing 1% by weight of zinc stearate based on the weight of polyester, is sprinkled on to the glass fibre in an amount of 7% by weight based on the weight of glass fibre.

The mixture is passed through an oven for 1 minute, the temperature varying from 2000C at the start to 1 700C at the finish. The mixture leaves the oven at a temperature of 1 300C and passes through water-cooled rollers to yield a bonded glass fibre mat containing 45% by weight polyester based on the weight of the glass fibre.

EXAMPLE 2 Haphazardly arranged chopped strands of glass fibre of average length 5 cm are placed on a conveyor belt at a density of 350 grams per square metre. A powdered polyester of molecular weight 1250 which is the reaction product of equimolar proportions of phthalic anhydride and isophthalic acid with neopentyl glycol and containing 1% by weight of zinc stearate based on the weight of the polyester, is sprinkled on the glass fibre in an amount of 5% by weight based on the weight of the glass fibre. The polyester was prepared as in Example 1 a except that 3 moles of phthalic anyhydride and 3 moles of isophthalic acid were used instead of the 6 moles of phthalic anhydride.

The mixture is passed through an oven of 1.5 minutes, the temperature varying from 2000C to 1 700C at the finish. The mixture leaves the oven at a temperature of about 1 300C and passes through water cooled rollers to yield a bonded glass fibre mat containing about 3% by weight polyester based on the weight of the mat.

Claims

1. A glass fibre product comprising short lengths of glass fibre bonded together by a binder polyester which is saturated and is the reaction product of an aromatic dicarboxylic acid or anhydride or mixtures thereof and neopentyl glycol, and has a molecular weight up to 5000.

2. A glass fibre product as claimed in claim 1 in which the glass fibres are haphazardly arranged.

3. A glass fibre product as claimed in claim 1 or claim 2 in which the glass fibres are arranged in chopped strands of lengths of 1 to 12 cm at a density of from 250 to 750 grams per square metre.

4. A glass fibre product as claimed in any of the preceding claims in which the amount of binder polyester in the bonded glass fibre product is from 1 to 20% by weight based on the weight of the product.

5. A glass fibre product as claimed in any preceding claim in which the aromatic dicarboxylic acid or anhydride is phthalic acid or anhydride, isophthalic acid, tetrabromophthalic anhydride or tetrachlorophthalic anhydride.

6. A glass fibre product as claimed in any preceding claim in which the aromatic dicarboxylic acid or anhydride is phthalic acid or anhydride or a mixture of one or both of these isophthalic acid.

7. A glass fibre product as claimed in any of the preceding claims in which the molecular weight of the polyester is from 1 500 to 4000.

8. A glass fibre product as claimed in any of the preceding claims in which the melting point of the binder polyester is from 50 to 1400C.

9. A glass fibre product as claimed in any of the preceding claims in which the binder polyester is soluble in at least one component of unsaturated polyester resinous compositions which may subsequently be reinforced with the bonded glass fibre product.

10. A glass fibre product as claimed in claim 9 in which the binder polyester is soluble in a vinyl monomer.

1 A glass fibre product as claimed in claim 10 in which the vinyl monomer is styrene.

12. A glass fibre product as claimed in claim 10 or 11 in which the refractive index of the polyester as a 50% solution in vinyl monomer is approximately similar to that of both the glass fibre and the unsaturated polyester resin which is subsequently reinforced with the glass fibre product.

13. A bonded glass fibre product substantially as described in either of the foregoing Examples.

14. A method for producing a glass fibre product as claimed in claim 1, which comprises applying a powdered binder polyester, which is saturated and is the reaction product, of an aromatic dicarboxylic acid or anhydride and neopentyl glycol, and has a molecular weight up to 5000, to short lengths of glass fibres, heating to a temperature above the melting point of the polyester and subsequently cooling to bind the material.

1 5. A method as claimed in claim 14 substantially as described in either of the foregoing Examples.

1 6. A glass fibre product whenever prepared by a method as claimed in claim 14 or claim

15.