EP1112303A2

EP1112303A2 - Curing of resins

Info

Publication number: EP1112303A2
Application number: EP99946287A
Authority: EP
Inventors: Darren Miles Bates
Original assignee: Chemcolloids Ltd
Current assignee: Chemcolloids Ltd
Priority date: 1998-09-12
Filing date: 1999-09-10
Publication date: 2001-07-04
Also published as: GB9909763D0; NO20011212D0; NO20011212L; CA2343392A1; AU5870799A; CN1325418A; WO2000015694A3; WO2000015694A2; JP2002524634A

Abstract

A method of manufacturing a product comprising at least two parts includes the steps of coating one of the parts at least partially with a resin having a trapped catalyst distributed therein, placing the parts together with the resin therebetween and releasing the catalyst into the resin to initiate curing at the desired time. The catalyst may be trapped either by encapsulation or by absorption/adsorption into the structure of a suitable substrate such as almond shell. The catalyst may be an organic peroxide, formic acid or toluene sulphonic acid. An accelerator may be used to accelerate curing.

Description

CURING OF RESINS

The present invention relates to a method of controlling the curing of

a resin and to a resin modified to provide such control. The invention also

includes the application of the method and the use of the resin in the

production of articles.

In the production of plywood, for example, individual layers of wood

are coated with resin, pressed together and subjected to heat in order to

cure the resin. The time for which the heat is supplied to obtain a cure can

be considerable slowing down the production process. Curing times can be

reduced by mixing a catalyst with the resin, but this may interfere with the

production process itself as curing may start either before or during the

application of the resin.

According to one aspect of the present invention, there is provided

a method of curing a resin including the steps of trapping a catalyst which

when released into the resin initiates curing, mixing the trapped catalyst

with the resin and releasing the catalyst into the resin to initiate curing at

the desired time.

According to another aspect of the present invention, there is

provided a method of manufacturing a product comprising at least two parts

including the steps of coating one of the parts at least partially with a resin having a trapped catalyst distributed therein, placing the parts together with

the resin therebetween and releasing the catalyst into the resin to initiate

curing at the desired time.

The invention also includes products made by the above method and

resins with distributed catalysts for use in the above methods.

The catalyst may be trapped either by encapsulation or by

adsorption/absorption into the structure of a suitable substrate such as

almond shell.

The resin may be any of the following Polyester resin. Vinyl

esterresin. Phenol formaldehyde resin, Epoxy resin. Acrylic resin,

melamine/urea formaldehyde resin. Phenolic resin.

The catalyst may be any appropriate catalyst such as:-

Organic peroxides for example Di benzoyl peroxide. Methyl ethyl keto-

peroxide, Cumene hydroperoxide, Acetylacetone peroxide (sold under trade

name Triganox 44B), tert-Butyl peroxybenzoate (sold under trade name

Triganox C), tert-Butyl-2-ethyl hexanoate (sold under trade name Triganox

21 ), tert-Butylperoxy-3,5,5, trimethyl hexanoate (sold under trade name

Triganox 42s), Cumene hydroperoxide (sold under trade name Triganox

K-80), Biz (4-tert-butylcyclohexyi-peroxdicarbonate) (sold under trade name

Perkadox 16). Amine Catalysts for example: Diethyltetra amine. Triethylamine Isocyanates, Boron tri fluoride, UV Curing Catalysts, Alkyl

Carbonates for example: Propylene and Ethylene carbonate, and mineral and

organic acids such as Formic acid, toluene sulphonic acid, or sulphuric acid.

The encapsulating material may be any one of the following; gelatine,

thermoset resins, fats, waxes, thermoplastics, polymeric compounds, or

silane compounds or any of the encapsulation materials disclosed in the

applicants copending international application published under publication

No. WO 98/26865.

Accelerators may also be used such as Colbait octoate (sold under

trade name NL-49-P), Diethylaniline (sold under trade name NL-64-10P).

Ammonium Sulphate or Ammonium Chloride.

The size of the encapsulated or coated particles may lie in the range

0.5 to 1000 microns.

Embodiments of the invention will now be described, by way of

example.

In a first embodiment, which relates to the manufacture of plywood,

layers of plies of wood are coated with resin, placed together with the resin

sandwiched between adjacent plies and subject to pressure urging them

together and/or heat to cure the resin so that the plies adhere strongly

together. In the conventional methods of production pressure and heat may have to be applied for a considerable period of time, for example, several

minutes, adding to the production time and to the expense of production.

In accordance with the invention, a catalyst is distributed through the resin.

The catalyst is distributed through the resin. The catalyst which may be

propylene carbonate, ethyiene carbonate or any other suitable catalyst

initiates curing of the resin to produce a bond between adjacent plies of

wood. However, if curing is initiated too early or progresses too quickly,

it may be difficult or impossible to carry out the manufacturing process

satisfactorily and/or efficiently. For example, if curing is already proceeding

when the plies are coated with resin it may not be possible to coat the plies

readily and, even if it is, the strength of the bond between plies may be

adversely affected.

In order to overcome this possible disadvantage, the release of the

catalyst into the resin to initiate curing is controlled by encapsulating the

catalyst. Encapsulation is achieved by irradiating the catalyst with

ultrasound in the presence of an encapsulating material to produce

microcapsules of catalyst coated with encapsulating material. The coating

isolates the catalyst from the resin even though the encapsulated resin

capsules are distributed through the resin. In this state, the resin may be

applied to the plies of wood as described previously, but curing will not begin and will therefore not affect this process until the granules are

ruptured to release the catalyst into the resin. Rupturing may be effected

by irradiating the capsules with ultrasound or by heat or any other suitable

method.

In an alternative method of encapsulation, catalyst is adsorbed into

the surface of granules of an inert substance which are coated with an

encapsulating material again by irradiating with ultrasound. In both cases

the size of the coated particles would generally lie in the range 0.5 to 1000

microns.

The catalyst may be any of the following materials, or any mixture

thereof:-

Organic peroxides for example Di benzoyl peroxide. Methyl ethyl keto-

peroxide, Cumene hydroperoxide, Acetylacetone peroxide (sole under trade

name Triganox 44B), tert-Butyi peroxybenzoate (sold under trade name

Triganox C, tert-Butyl-2-ethyl hexanoate (sold under trade name Triganox

21), tert-Butylperoxy-3,5,5, trimethyl hexanoate (sold under trade name

Triganox 42s), Cumene hydroperoxide (sold under trade name Triganox

K-80), Biz (4-tert-butylcyclohexyl-peroxdicarbonate) (sold under trade name

Perkadox 16). Amine Catalysts for example: Diethyltetra amine,

Triethylamine Isocyanates, Boron tri fluoride, UV Curing Catalysts, Alkyl Carbonates for example: Propylene and Ethylene carbonate and mineral and

organic acids such as Formic acid, toluene sulphonic acid, or sulphuric acid.

Accelerators may also be used such as Colbalt octoate (sold under

trade name NL-49-P), Diethylaniline (sold under trade name NL-64-10P).

The encapsulating material may be any one of the following or any

mixture thereof:- gelatine, thermoset resins, fats, waxes, thermoplastics,

polymeric compounds, or silane compounds or any of the encapsulation

materials disclosed in the applicants copending international application

published under publication No. WO 98/26865.

The resin may be any one of the following or any mixture thereof :-

Polyester resin. Vinyl esterresin. Phenol formaldehyde resin, Epoxy resin.

Acrylic resin, meiamine/urea formaldehyde resin. Phenolic resin.

In a second embodiment, a catalyst is trapped by absorption into a

suitable substrate rather than by adsorption as previously described. A

suitable substrate is almond shell which has a surface which facilitates

absorption/adsorption of catalyst into its porous structure. The catalyst is

formic acid and the resin is a melamine/urea formaldehyde resin although

other catalysts and resins, for example, as detailed above may be used.

The process for making the almond shell formic acid/toluene

sulphonic acid catalyst material is as follows. i) The formic acid/toluene sulphonic acid is first

dissolved/dispersed in/into acetone. Acetone acts as a carrier solvent

for the acid catalyst into the porous structure of the almond shell.

ii) almond shell is then added to the acid/acetone mixture.

iii) The acid/acetone/almond shell mixture is sonicated using a

20kHz, 400 Watt ultrasonic probe for 3-5 minutes until the

acetone/acid has absorbed/adsorbed into the almond shell structure.

This process can be easily observed by a significant thickening

appearance of the mixture. One of the reasons a solvent is used is

in order for ultrasound to work effectively with a high solid almond

shell content present. Excess liquid is required (i.e. acetone) in

which cavitation can develop. When the cavitation bubbles collapse,

a large energy source/shock wave is created and it is this energy

which drives the liquid mixture into the almond shell structure.

iv) The acetone solvent is removed from the slurry mixture using

drying methods leaving just the acid catalyst embedded in the almond

shell. The acetone may be removed and re-cycled using condensers.

The almond shell/acid catalyst product is a fairly free flowing powder

which can be easily dispersed in resin.

Acetone is used as a solvent because; a) It has very good dissolving properties. For example, para

toluene sulphonic acid catalyst (PTSA) which is a solid powder,

needs to be dissolved in the acetone before it can be driven into the

almond shell.

b) It has a very low boiling point which facilitates its removal

during the drying process at low temperature. This is a very

important characteristic when formic acid is used because this

catalyst has a relatively low boiling point and therefore if high drying

temperatures were used, the formic acid would be removed as well.

c) The presence of acetone in the sonication process keeps the

temperature very low (specific heat capacity characteristic) reducing

or eliminating vaporisation problems.

When the almond shell/acid catalyst is dispersed with the resin, the

molecules of the resin are so large that they cannot access the almond shell

structure very easily or quickly and therefore cannot come into contact with

the acid catalyst which is embedded in the structure. Curing of the resin

will therefore not begin. The acid catalyst can be activated by heat. This

will cause the structure to expand and open up allowing the resin to get at

the catalyst. It needs to be noted that this is not an encapsulation

technology and no coating has been used. However a coating could be applied if the end user/application required much greater pot-life stability.

It will be appreciated that the above embodiments have been

described by way of example only and that many variations are possible

without departing from the scope of the invention. For example, the

method of the invention may be applied to any product manufacture where

one or more parts are coated and/or impregnated with a curable resin either

to enable the parts to be secured together or as part of the production

process.

Felts or glass fibre may be impregnated with a curable resin of the

invention formed into a desired shape and the resin then cured. Material

may be supplied pre-impregnated with resin for use in a downstream

production process. These material composites could be employed in the

following general areas:-

i) Boat construction,

ii) Automotive industry - for example interior/exterior components

and body panels,

iii) Train/Aeorplane construction - for example interior/exterior

components and body panels,

iv) Off shore marine/oil drilling applications,

v) Building construction - wall panels (interior/exterior), roofing vi) House-hold goods,

vii) Surface coatings

viii) Fire retardent foams/coatings/composites,

ix) Binders for the paint and paper industry,

x) Binders for use in the foundry industry,

xi) Filament windings,

xii) Plastic extrusions,

xiii) Adhesives,

xiv) MDF/Particle Board,

xv) Dough Moulding compounds,

xvi) Pre-impregnated products,

xvii) Binders for concrete applications used in the

building/construction industry.

Claims

1. A method of curing a resin including the steps of trapping a catalyst

which when released into the resin initiates curing, mixing the trapped

catalyst with the resin and releasing the catalyst into the resin to initiate

curing at the desired time.

2. A method of manufacturing a product comprising at least two parts

including the steps of coating one of the parts at least partially with a resin

having a trapped catalyst distributed therein, placing the parts together with

the resin therebetween and releasing the catalyst into the resin to initiate

curing at the desired time.

3. A method as claimed in claim 1 or 2, in which the catalyst is trapped

by encapsulation.

4. A method as claimed in claim 3, in which the encapsulation material

comprises one or more of the following :-

gelatine, thermoset resins, fats, waxes, thermoplastics, polymeric

compounds, or silane compounds or any of the encapsulation materials

disclosed in the applicants copending international application published

under publication No. WO 98/26865.

5. A method as claimed in 1 or 2, in which the catalyst is trapped by

absorption/adsorption.

6. A method as claimed in claim 5 in which the catalyst is trapped by

absorption/adsorption into the surface of almond shell.

7. A method as claimed in any of claims 1 to 6, in which the resin

comprises one or more of the following Polyester resin. Vinyl esterresin,

Phenol formaldehyde resin, Epoxy resin. Acrylic resin, melamine/urea

formaldehyde resin. Phenolic resin.

8. A method as claimed in any preceding claim, in which the catalyst is

an organic peroxide.

9. A method as claimed in any of claims 1 to 7, in which the catalyst

comprises one or more of the following :-

Organic peroxides for example Di benzoyl peroxide. Methyl ethyl keto-

peroxide, Cumene hydroperoxide, Acetylacetone peroxide (sold under trade

name Triganox 44B), tert-Butyl peroxybenzoate (sold under trade name

Triganox C), tert-Butyl-2-ethyl hexanoate (sold under trade name Triganox

21 ), tert-Butylperoxy-3,5,5, trimethyl hexanoate (sold under trade name

Triganox 42s), Cumene hydroperoxide (sold under trade name Triganox

K-80), Biz (4-tert-butylcyclohexyl-peroxdicarbonate) (sold under trade name

Perkadox 16). Amine Catalysts for example: Diethyltetra amine,

Triethylamine isocyanates. Boron tri fluoride, UV Curing Catalysts, Alkyl

Carbonates for example: Propylene and Ethylene carbonate, and mineral and organic acids such as Formic acid, toluene sulphonic acid, or sulphuric

acid.

10. A method of trapping formic acid catalyst in almond shell including

the steps of dissolving of dispersing formic acid into acetone, adding

almond shell to the acid/acetone mixture and sonicating the mixture until

the acetone and mixture has been absorbed/adsorbed into the almond shell

structure.

11. A method of trapping toluene sulphonic acid catalyst in almond shell

including the steps of dissolving or dispersing toluene sulphonic acid into

acetone, adding almond shell to the acid/acetone mixture and sonicating the

mixture until the acetone acid mixture has been absorbed/adsorbed into the

almond shell structure.

12. A method of trapping as claimed in claim 10 or 11, in which the

acid/acetone mixture is sonicated using a 20 KHz 400 watt ultrasonic probe

for 3 to 5 minutes.

13. A method of curing a resin including the steps of trapping a catalyst

which when released into the resin initiates curing, mixing the trapped

catalyst with the resin and releasing the catalyst into the resin to initiate

curing at the desired time in which the catalyst is trapped by the method

claimed in claim 10, 1 1 or 12.

14. A method as claimed in any of claims 1 to 9 or 13 in which an

accelerator is used to accelerate curing.

15. A method as claimed in claim 14, in which the accelerator is Cobalt

octoate (sold under trade name NL-49-P), Diethylaniline (sold under trade

name NL-64-10P). Ammonium Sulphate or Ammonium Chloride.

16. A product made by the method as claimed in any preceding claim.