WO2000046306A1

WO2000046306A1 - Timber process and product

Info

Publication number: WO2000046306A1
Application number: PCT/ZA2000/000019
Authority: WO
Inventors: Sydney Maboka
Original assignee: Sappi Limited
Priority date: 1999-02-08
Filing date: 2000-02-08
Publication date: 2000-08-10
Also published as: CA2361618A1; EP1161498A1; AU3008600A

Abstract

This invention provides a binding mixture for use in manufacturing chipboard, the mixture including an effective amount of methyl di-isocyanate ('MDI') and one or more polyurethane catalyst(s) being selected from the following: (a) one or more amine compound(s) including aliphatic and aromatic tertiary amine derivatives of phenols, esters, ethers, alkenes and/or alcohols; or (b) one or more organometallic compounds of tin, bismuth, zinc, iron, and/or alkali metal salt(s); or (c) suitable mixtures of (a) and (b) above.

Description

TIMBER PROCESS AND PRODUCT

INTRODUCTION

This invention relates to a timber process and product. More particularly

this invention relates to a process for manufacturing so-called particle

board or chipboard, and to a timber product in the form of such particle

board or chipboard when manufactured by or from the aforementioned

process.

BACKGROUND TO THE INVENTION

It is known in the manufacture of particle board or chipboard (hereinafter

referred to as "chipboard") that a urea-formaldehyde resin (hereinafter

referred to as "UF") is used as a binder or adhesive to bond the particles

or chips of wood.

Typically such binders contain approximately 55% to 60% formaldehyde

(in moles) but because of recent awareness of the health problems

associated with the use of formaldehyde, the amount of formaldehyde in

such resins is generally being reduced. Hence the amount of

formaldehyde in the aforementioned resins has been reduced to

approximately 50% or less (in moles). The aforementioned resins need to be cured, and the curing process is

accelerated by heating in a press under pressure i.e. heat is applied by

hot metal platens on both sides of a so-called mat of glued chips. Such

chipboard pressing takes place either in a batch-type (using daylight

presses) or in a continuous process i.e. using continuous (for example

roller) presses.

It is also known in the chipboard industry that methyl di-isocyanate

(hereinafter referred to as "MDI") may be added to the aforementioned

type of resin to hasten the curing process i.e. to effectively increase the

speed of the curing process and hence to reduce the curing time.

However, because of the high cost of MDI and the amount required to

effectively hasten the curing process, the use of MDI is not cost-

effective on an industrial scale.

OBJECTS OF THE INVENTION

It is accordingly a general object of the present invention to provide an

improved binding mixture for chipboard manufacture. It is also an object of the present invention to provide an improved

process in which such improved mixture is used, which is both cost-

effective and which increases the efficiency and rate of curing of the

binding mixture.

It is a further object of the invention that the aforementioned binding

mixture and process will lead to an increase in productivity or production

flowing from shorter curing periods resulting from use of the

aforementioned binding mixture.

SUMMARY OF THE INVENTION

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

binding mixture for use in manufacturing chipboard, the mixture including

an effective amount of MDI and one or more polyurethane catalyst(s)

being selected from the following:

(a) one or more amine compound(s) including aliphatic and aromatic

tertiary amine derivatives of phenols, esters, ethers, alkenes and/or

alcohols; or

(b) one or more organometallic compound(s) of tin, bismuth, zinc, iron

and/or alkali metal salt(s); or

(c) suitable mixtures of (a) and (b) above. The MDI may or may not be water-emulsifiable, and the or each

polyurethane catalyst(s) may or may not be (a) delayed-action catalyst(s).

To the mixture may be added an effective amount of toluene di-

isocyanate ("TDI") and/or one or more internal wetting and release

agents.

The aforementioned mixture(s) may of course include a suitable amount

of urea-formaldehyde resin which may or may not have suitable

quantities of polyol(s) added thereto.

The amount of formaldehyde in the aforementioned urea-formaldehyde

resin may preferably be approximately 50% (in moles) i.e. may be less

than, equal to, or more than 50% (in moles).

By using a catalyst as aforesaid, the effective amount of MDI required is

reduced relative to the amounts known in the prior art to be sufficient to

hasten the curing process of the mixture.

Suitable amines or amine compounds may be selected from the

following: 2-dimethyl ethanolamine (hereinafter referred to as "DMEA");

di-amino bicyclo-octane (hereinafter referred to as "DABCO"); and

N,N-dimethyl cyclohexylamine (hereinafter referred to as "DMCHA").

Suitable organometallic tin-based compounds may be selected from the

following:

stannous octoate, dibutyl tin dilaurate, dibutyl tin mercaptide, dibutyl tin

thiocarboxylate, and dioctyl tin thiocarboxylate.

Other suitable organometallic compounds may include ferric

acetylacetonate.

Suitable alkali metal salts may be selected from the following:

calcium carbonate, salts of carbonic acid, and salts of acetic acid.

One supplier of the above catalysts (as mixtures or single compounds) is

Air Products, South Africa, and the catalysts may be identified inter alia

by the following trade marks/brands and/or acronyms, respectively:

When used with one or more of the above catalysts, the amount of MDI

required to effect a suitable hastening of the curing process may

preferably be in the range of about 0.1 % to 1 .9% on bone dry wood

(hereinafter referred to as "BDW").

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

an additive for a binding mixture for use in manufacturing chipboard, the

additive including an effective amount of MDI and a catalyst, each as

indicated above, and as otherwise described herein.

According to a further aspect of the present invention, there is provided

a process for manufacturing chipboard, the process including the steps of adding to or using in a binding mixture consisting of urea-formaldehyde

resin, an effective amount of MDI and a catalyst, each catalyst being as

indicated above, or as otherwise herein described, or an additive,

respectively, as herein described, and suitably mixing the binding mixture

with wood particles and/or chips.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described in greater detail by way of non-

limiting example(s), with reference to the following:

1 . LABORATORY TESTS

Laboratory tests were carried out by way of reasonable technical trials,

by personnel of the applicant's wholly owned subsidiary namely Sappi

Timber Industries (Proprietary) Limited on wood particles and chips as

used for manufacturing chipboard in the factories of the aforementioned

company.

Using the aforementioned raw materials, binder mixtures of urea-

formaldehyde resin as typically used in the aforementioned company's

production facilities were applied to the aforementioned particle chips. and compared with urea-formaldehyde mixtures including MDI, and

further compared with mixtures of urea-formaldehyde with MDI and

various catalysts as set out above.

The resulting mixtures of particles/chips and binder mixtures were

pressed in a laboratory scale press to simulate plant production

conditions, and curing times were measured. In the binding mixtures

that did not include a catalyst, longer curing times were observed.

Details of the mixtures used and the corresponding results are set out in

Table 1 hereafter:

TABLE 1

Table 1 (Contd)

CATALYSTS

(a) 1.4% (on BDW) MDI modified with 45.8 PPG Triol MDI pre-polymer + 0.1% DABCO TMR 2 catalyst

(b) 1.4% (on BDW) MDI modified with 44.3 PPG Triol MDI pre-polymer + 0.1% (on UF mass) DABCO K 15 catalyst

(c) 1.4% (on BDW) MDI modified with 44.3 PPG Triol MDI pre-polymer + 0.1% (on UFmass) DABCO DC 2 catalyst

(d) 1.2% (on BDW) MDI modified with 42.3 PPG Triol MDI pre-polymer + 0.1% (on UFmass) DMCHA catalyst

(e) (1.2% (on BDW) MDI modified 42.3 with PPG Triol MDI pre-polymer + 0.1% (on UF mass) DABCO R8020 catalyst

CD 1.2% (on BDW) MDI modified with 40.0 PPG Triol MDI pre-polymer + 0.1% (on UF mass) Thorcat catalyst

(g) 1.4% (on BDW) MDI modified with 42.8 Polyethylene glycol MDI pre- polymer + 0.1% (on UF mass) DABCO DC 2 catalyst

(h) 0.5% (on BDW) MDI + 1.1% (on 33.3 UF mass) DMEA catalyst

(0 0.5% (on BDW) water emulsified 33.3 MDI + 1.1% (on UF mass) DMEA catalyst In the aforementioned table, the brand name Daltolac R130 is a brand

name for polyether polyol, which is sold by ICI (Imperial Chemical

Industries). Similarly PPG diol MDI Pre-Polymer is the brand name for

polypropylene glycol diol MDI pre-polymer and PPG triol TDI Pre-Polymer

is the brand name for polypropylene glycol triol TDI pre-polymer.

The curing times for mixtures where typically 0.1 % to 1 .9% MDI and

one or more of the abovementioned catalysts were added (on BDW),

were the shortest.

The results of the above tests indicated that in all cases the binding

mixtures with MDI and one or more catalysts resulted in a shorter curing

period with the same or an increased binding strength.

It was also found that the use of amines as catalysts alone resulted in

the least costly mixture and hence the most cost-effective process(es).

2- PRODUCTION-PLANT TRIALS

The aforementioned tests were repeated by way of reasonable technical

trials, on two different production lines namely one using a single

daylight press and the other using a continuous press. Details of the mixtures used and the corresponding results are set out in Table 2

hereunder:

TABLE 2

The abovementioned production-line tests confirmed the aforementioned

laboratory results, with improvements in or increased curing times of up

to approximately 14 to 24% . The applicant believes that it may be

possible to achieve greater improvements than the aforementioned.

It will therefore be seen from the aforementioned that a considerable

improvement in curing times and hence in productivity may be possible

by using the aforementioned invention. Such improvement also appears

to be cost-effective relative to increased productivity and production on

an industrial scale. Although certain embodiments only of the invention have been described

herein, it will be apparent to any person skilled in the art that other

variations and/or modifications of the invention are possible. Such

variations and/or modifications are therefore to be considered as falling

within the spirit and scope of the invention as claimed hereinafter.

Claims

1 . A binding mixture for use in manufacturing chipboard, the mixture

including an effective amount of methyl di-isocyanate ("MDI") and

one or more polyurethane catalyst(s) being selected from the

following:

(a) one or more amine compound(s) including aliphatic and

aromatic tertiary amine derivatives of phenols, esters,

ethers, alkenes and/or alcohols; or

(b) one or more organometallic compounds of tin, bismuth,

zinc, iron, and/or alkali metal salt(s); or

(c) suitable mixtures of (a) and (b) above.

2. A binding mixture as claimed in claim 1 , wherein the MDI is water-

emulsifiable.

3. A binding mixture as claimed in either claim 1 or claim 2, wherein

the or each polyurethane catalyst(s) is/are (a) delayed-action

catalyst(s).

4. A binding mixture as claimed in any one of the preceding claims,

wherein an effective amount of toluene di-isocyanate ("TDI") is

added to the MDI.

5. A binding mixture as claimed in any one of the preceding claims,

wherein one or more internal wetting and release agents is/are

added to the mixture.

6. A binding mixture as claimed in any one of the preceding claims,

wherein a suitable amount of urea-formaldehyde resin is added.

7. A binding mixture as claimed in claim 6, wherein a suitable

quantity of or more one polyol(s) is/are added.

8. A binding mixture as claimed in either claim 6 or claim 7, wherein

the amount of formaldehyde in the urea-formaldehyde resin may

be approximately 50% (in moles).

9. A binding mixture as claimed in any one of the preceding claims,

wherein the or each suitable amine(s) or amine compound(s) are

selected from the following:

2-dimethyl ethanolamine ("DMEA");

di-amino bicyclo-octane ("DABCO"); and

N,N-dimethyl cyclohexylamine ("DMCHA").

10. A binding mixture as claimed in any one of the preceding claims,

wherein the or each suitable organometallic tin-based compound(s)

is/are selected from the following:

Stannous octoate, dibutyl tin dilaurate, dibutyl tin mercaptide,

dibutyl tin thiocarboxylate, and dioctyl tin thiocarboxylate.

1 1 . A binding mixture as claimed in any one of the preceding claims,

wherein the suitable organometallic compounds include ferric

acetylacetonate.

12. A binding mixture as claimed in any one of the preceding claims,

wherein the suitable alkali metal salts are selected from the

following:

calcium carbonate, salts of carbonic acid, and salts of acetic acid.

13. A binding mixture as claimed in any one of the preceding claims,

wherein the amount of MDI required to effect a suitable hastening

of the curing process is in the range of from about 0.1 % to 1 .9%

of bone dry wood ("BDW").

14. A binding mixture substantially as herein described and/or

exemplified.

15. An additive for a binding mixture for use in manufacturing

chipboard, the additive including an effective amount of MDI and a

catalyst, each catalyst being as claimed in any one of the

preceding claims.

16. An additive for a binding mixture for use in making chipboard,

substantially as herein described and/or exemplified.

17. A process for manufacturing chipboard, the process including the

steps of adding to or using in a binding mixture an effective

amount of MDI and a catalyst, each catalyst being as claimed in

any one of claims 1 to 14, and suitably mixing the binding mixture

with wood particles and/or chips.

18. A process for manufacturing chipboard, the process including the

steps of adding to or using in a binding mixture an effective

amount of an additive as claimed in either claim 15 or claim 16,

and suitably mixing the binding mixture with wood particles and/or

chips.

19. A process for manufacturing chipboard, substantially as herein

described and/or exemplified.