Glass strand structure designed to reinforce bonded abrasive articles

Abstract

A structure based on glass strand coated with a resin composition containing, by weight percent of solid matter: from 75 to 98% of a mixture of a first novolac having a glass transition temperature lower than or equal to 60 C. and a second novolac having a glass transition temperature above 60 C.; from 0.5 to 10% of a wax; from 1 to 15% selected from an imine and a modified melamine of formula (I): ##STR00001##
where R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 are each independently H, CH.sub.2OH, CH.sub.2OCH.sub.3, or CH.sub.2OCH.sub.2OCH.sub.3 radical, with at least one of R.sub.1 to R.sub.6 not being H; and from 0 to 10% of a plasticizing agent. Also, a resin composition for producing a reinforcing structure and bonded abrasive articles incorporating such a structure.

Claims

1. A glass strand structure comprising continuous glass strands in the form of a web, a mat, a mesh, or a fabric, or cut glass strands in the form of a mat, wherein the web, mat, mesh, or fabric comprises a coating comprising a resin composition, wherein the resin composition comprises, by weight percent of solid matter of the resin composition: from 75 to 98% of a mixture comprising a first novolac having a glass transition temperature lower than or equal to 60 C. and a second novolac having a glass transition temperature above 60 C.; from 0.5 to 10% of a wax; from 1 to 15% of at least one crosslinking agent selected from the group consisting of an imine and modified melamine of formula (I): ##STR00003## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 are each independently a hydrogen atom, or a CH.sub.2OH, CH.sub.2OCH.sub.3, or CH.sub.2OCH.sub.2OCH.sub.3 radical, where at least one of the radicals R.sub.1 to R.sub.6 is not H; and from 0 to 10% of a plasticizing agent, wherein the first and second novolacs are obtained by reacting phenol and formaldehyde in a formaldehyde/phenol molar ratio in a range from 0.75 to 0.85.

2. The structure of claim 1, wherein the first novolac is 10 to 50% by weight of the mixture of novolacs.

3. The structure of claim 1, wherein the first novolac has a glass transition temperature greater than 20 C.

4. The structure of claim 1, wherein the second novolac has a glass transition temperature above or equal to 80 C.

5. The structure of claim 1, wherein the wax is a paraffin wax or an ethylenebisamide wax.

6. The structure claim 1, wherein the wax content does not exceed 3% by weight of solid matter of the resin composition.

7. The structure of claim 1, wherein at least one of the radicals R.sub.1 to R.sub.6 is equal to CH.sub.2OCH.sub.3.

8. The structure of claim 1, wherein the crosslinking agent is selected from the group consisting of hexamethylenetetramine and hexamethoxymethylmelamine.

9. The structure of claim 1, wherein the content of crosslinking agent is 3 to 9%, by weight of solid matter of the resin composition.

10. The structure of claim 1, wherein the plasticizing agent is an alkylphosphate, a phthalate, triethanolamine, an oil, a polyhydric alcohol, or any mixture thereof.

11. The structure of claim 1, wherein the plasticizing agent content does not exceed 3% by weight of solid matter of the resin composition.

12. The structure of claim 1, comprising the continuous glass strands in the form of a web, a mat, a mesh, or a fabric.

13. The structure of claim 12, wherein the continuous glass strands have a diameter varying from 9 to 24 m.

14. The structure of claim 12, wherein the continuous glass strands have a count (or linear mass) of between 34 and 4800 tex.

15. The structure of claim 1, comprising the continuous glass strands in the form of a fabric having a grammage varying from 100 to 1000 g/m.sup.2.

16. A bonded abrasive article, comprising: abrasive particles bonded with a binder; and the glass structure of claim 1.

17. The article of claim 16, in the form of an abrasive grinding wheel.

Description

EXAMPLES 1 TO 7

(1) Resin compositions were prepared comprising the constituents listed in Table 1.

(2) Each resin composition was used to impregnate a fabric composed of glass strands ((leno weave; warp strand EC 204 tex s/z; weft strand RO 408 tex; No. COUNTS (10 cm): weft 235%, warp 245% (2)) which was then dried at 140 C. for 1 minute in an oven.

(3) The properties of the glass fabric are listed in Table 1.

EXAMPLE 8

(4) This example illustrates the application of the resin composition in an industrial installation.

(5) A glass strand fabric described in Examples 1 to 7, 0.5 m wide, unwound from a reel, was disposed on an industrial coating line operating continuously. On its path, the fabric passed into an impregnating bath containing the resin composition of Example 1 and was then treated in an oven comprising a first section heated to 135 C., and a second section heated to 115 C., before being collected in the form of a reel.

(6) The glass strand fabric had the following properties: Amount of dust: 0.8% Tensile strength: warp: 3100 N/5 cm; weft: 3500 N/5 cm Adhesive power after 30 days: 1.5 Loss on ignition: 30%

(7) TABLE-US-00001 TABLE 1 6 7 Example 1 2 3 4 5 (comparative) (comparative) Phenol-formaldehyde novolac.sup.(1) 41.40 42.55 41.40 41.40 41.40 (60.3) 44.60 (67.4) 52.00 (78.8) (Tg around 80 C.) (64.4) (65.5) (62.2) (60.3) Phenol-formaldehyde novolac.sup.(2) 19.10 19.65 19.10 19.10 19.10 (27.9) 20.60 (31.1) 14.00 (21.2) (Tg around 40 C.) (29.7) (30.2) (28.7) (27.8) Polyethylene wax.sup.(3) 0.90 (1.4) 0.90 (1.4) 0.90 (1.3) 0.90 (1.3) 0.90 (1.3) 1.00 (1.5) Hexamethylenetetramine.sup.(4) 2.90 (4.5) 1.90 (2.9) Hexamethoxymethylmelamine.sup.(5) 5.25 (7.8) Hexamethoxymethylmelamine.sup.(6) 7.25 (10.6) Hexamethoxymethylmelamine.sup.(7) 7.20 (10.5) Water 5.25 3.70 2.90 0.90 0.90 1.00 Alcohol 30.45 31.30 30.45 30.45 30.45 32.80 34.00 Flexibility (mN) 160 130 155 160 170 110 n.d. Adhesive power T = 0 2.5 2.0 2.0 2.0 2.5 2.5 4.0 T = 15 days 2.0 2.2 1.5 1.5 2.5 2.0 3.5 T = 30 days 1.5 1.5 1.5 1.5 2.5 1.5 3.5 Tensile strength (N/5 cm) 3400 3000 3400 3200 2800 2200 2300 Between parentheses: % by weight of solid matter n.d.: not determined .sup.(1)sold under the reference Prefere 3E 5057E X-C 69 by DYNEA; solution having a concentration of 65% by weight of solid matter in ethanol .sup.(2)sold under the reference PF7505 IL by HEXION; solution having a concentration of 70% by weight of solid matter in ethanol .sup.(3)sold under the reference Hydrocer 69 by SHAMROCK; solution having a concentration of 50% by weight of solid matter in ethanol .sup.(4)sold under the reference Hexamine by HEXION; solution having a concentration of 40% by weight of solid matter in water .sup.(5)sold under the reference Cyrez 963L by CYTEC; 100% of hexamethoxymethylmelamine; solution having a concentration of 72% of solid matter in water .sup.(6)sold under the reference Cohedur A by CYTEC; 50% of hexamethoxymethylmelamine and 50% of mineral fillers; content of solid matter: 100% .sup.(7)sold under the reference Resamin HF480 by CYTEC; 100% of hexamethoxymethylmelamine; content of solid matter: 100%