EP3055374A1

EP3055374A1 - Wood adhesives for producing particle boards

Info

Publication number: EP3055374A1
Application number: EP14786363.3A
Authority: EP
Inventors: Antonio Pizzi; Marie-Christine LAGEL; Andreas Redl
Original assignee: Syral Belgium NV; Universite de Lorraine
Current assignee: Syral Belgium NV; Universite de Lorraine
Priority date: 2013-10-07
Filing date: 2014-10-07
Publication date: 2016-08-17
Also published as: WO2015052657A1; US10316224B2; FR3011554B1; FR3011554A1; CN105829480A; US20160369138A1; BR112016007254A2; US20190249046A1

Abstract

The present invention relates to a composition based on phenolic resin comprising at least one phenolic resin, a vegetable protein hydrolysate, preferentially a wheat gluten hydrolysate, and an agent for accelerating curing, and also to the process for the production thereof.

Description

Wood glues for the preparation of particle board

The present invention relates to a phenolic resin composition such as adhesive wood glue compositions. In particular, such compositions are used for the preparation of particle boards or fibers which meet the technical requirements enabling them to be used in a humid environment. At the same time, these panels must meet the technical requirements for formaldehyde emissions in which they can be classified in class El according to the European standard EN 312 relating to the requirements for particle board in application of the European directive DI 89 / 106 / EC 21/12/1988.

Particle board or fibreboard manufacturing is based on binding lignocellulosic fibers or particles with a binder. This binder is most often obtained from a synthetic glue containing formaldehyde. During use, the particle boards thus prepared tend to release formaldehyde. In 2005, formaldehyde was classified by the WHO as a carcinogen. Therefore, it is very important that the formaldehyde emissions from these wood panels be kept to a minimum. Here already, some efforts have been made to modify in this sense, formaldehyde-based resins, such as urea formaldehyde resins (UF-resins), melamine-urea-formaldehyde resins (MUF-resins) and Phenol-formaldehyde (PF -résines).

In addition, there are also different types of fiber board or particle board, which correspond to different quality requirements. Typical quality requirements are related to strength in combination with requirements for moisture resistance. In order to comply with these requirements, different resins are used. In the case where a good resistance to humidity is desired, it is preferable to use glues based on phenolic resins.

At the same time, there is also a desire to value biomass, a resource renewable, and replace products obtained from fossil fuels. In this context, the use of renewable resources in biobased adhesives is well known. Since the early 1900s, the use of soy flour adhesives has allowed plywood to become a cost-effective substitute for solid wood for interior applications. Adhesives have been improved to provide better water resistance, but they have never achieved sufficient moisture resistance to produce plywood of sufficient quality for outdoor use. Today, most of these biobased adhesives have been replaced by synthetic adhesives because of cost factors, durability and availability. With the rising cost of oil-based adhesives, soy flour-based adhesives are once again under consideration (Wescott and Frihart, 38th International Wood Composites Symposium Proceedings, 2004)

Compared with soy flour, other sources of protein are considered less attractive because of their availability and cost. Despite this, very little research has been done in the past with respect to other sources of protein. No successful solution has been proposed to provide resin compositions containing proteins that have sufficient moisture resistance.

The purpose of this patent application is therefore to provide a phenolic resin composition such as an adhesive composition of wood glue or a rigid phenolic foam comprising a protein component, in particular a vegetable protein component, which allows the manufacture of particle-based or wood-fiber-based articles, which may be used in a moist environment, and which meet the requirements of class El for the emission of formaldehyde according to EN 312. This means that the values of formaldehyde emission must be less than 6.5 mg / 100 g dry panel, as determined by the method described in standard EN 717-3. The internal cohesion in dry and wet conditions is expressed by specific internal binding values, determined according to EN 319 and EN 321 and the internal swelling after 24 hours according to EN 317. Values indicate whether the glue can be used to prepare particle boards or fibers, with the required properties.

The object of the invention is achieved by a phenolic resin-based composition, preferably an adhesive composition or a foam (typically a rigid foam) comprising at least one phenolic resin, a vegetable protein hydrolyzate, and an accelerating agent. curing.

In one embodiment of the invention, the vegetable protein hydrolyzate is obtained from a cereal protein, preferably wheat gluten.

In a preferred embodiment of the composition according to the invention, 10 to 25 mol% of the phenol of said phenolic resin is substituted with a vegetable protein hydrolyzate, and in that the phenol: aldehyde molar ratio is 1: 1. , 5 to 1: 1.7. When the phenolic resin is a phenol: formaldehyde resin, the adhesive composition comprises a phenolic resin, wherein 10 to 25 mol% of the phenol is substituted with a vegetable protein hydrolyzate, and so that the phenol: formaldehyde molar ratio is from 1: 1.5 to 1: 1.7. By "phenolic resin" according to the invention is meant any resinous reaction product of a phenol, such as phenol, resorcinol, phenol substituted with an alkyl group such as cresol, xylenol, p-tert -butylphenol and p-phenylphenol with an aldehyde, such as formaldehyde, acetaldehyde and furfuraldehyde. As an indication, an example of a phenolic resin is Plyophen J-325 or Phenolite J-325.

The phenolic resin in which the phenol is substituted with a vegetable protein hydrolyzate according to the invention can be obtained for example by mechanical mixing.

By "curing accelerating agent" is meant according to the invention an agent accelerating the curing of the phenolic resin such as a molecule comprising at least one ester functional group, typically a glycerol ester. For example, the agent accelerating the curing of the phenolic resin is chosen from triacetin, butyrolactone, caprolactone and propylene carbonate.

Triacetin or glyceryl triacetate (CAS No. 102-76-1) is a triester of glycerol and acetic acid. This triglyceride is obtained by esterification of natural glycerin. It can also be obtained from acetic anhydride in petrochemicals. Its chemical formula is C9H1406 and its molar mass of 218.21 g / mol.

In a more preferred embodiment, the triacetin content may vary between 4 and 10% by weight of the resin solids, preferably between 6 and 8%. Dry matter is measured by ISO 3251 method for varnish and plastic paints. More particularly, this measurement is carried out on samples with a mass of 3 ± 0.5 g, these samples are heated for 60 minutes at 135 ° C. and the dry matter is determined and expressed as a percentage by mass.

The plant protein hydrolyzate used can be obtained by acid hydrolysis, alkaline or enzymatic hydrolysis or a combination thereof. In a preferred embodiment, acid and / or enzymatic hydrolysis of the proteins is used. Typically, the vegetable protein hydrolyzate is also deamidated. The hydrolysis and / or the deamidation of the gluten allow an increase in its solubility. Typically, hydrolysis and deamidation are obtained under acidic conditions.

As an indication, an acid hydrolysis can be implemented by the use of hydrochloric acid or sulfuric acid under conditions known to those skilled in the art.

As an indication, an enzymatic hydrolysis is implemented using proteolytic enzymes well known to those skilled in the art. Typically, gluten can be hydrolysed by pepsin and / or papain. Trypsin, chymosin, or chymotrypsin may also be used. Preferably, the hydrolyzate of wheat gluten is obtained by enzymatic hydrolysis and has an average molecular mass of between 3 and 20 kDa, preferably between 4 and 15 kDa. Preferably, the hydrolyzed protein has an average molecular mass of between 4.5 and 12 kDa, 5 and 10 kDa, typically between 5.5 and 8 kDa.

This average molecular weight can be determined for example by HPLC, size exclusion chromatography (SEC) or permeate gel chromatography (GPC) according to conditions well known to those skilled in the art.

Another object of the present invention is to provide a method for forming a phenolic resin composition typically a wood glue type adhesive composition, said method comprising the steps of:

mixing phenol and a vegetable protein hydrolyzate in the presence of a base solution and a 10% molar excess of formaldehyde in a mixer;

heating the resulting mixture to a temperature of 90-98 ° C and maintaining at that temperature for about 15 minutes to one hour; add additional formaldehyde to give a phenol: formaldehyde ratio of 1: 1, 5 to 1: 1, 7;

continue the reaction until a resin with a viscosity of between 0.5 and 0.8 Pa.s at 25 ° C is obtained;

mixing the obtained resin with a hardening accelerating agent.

The mixture according to the process of the invention can be carried out in any type of mixer.

The viscosity can be measured using a Brookfield DV-II + Viscometer viscometer at a speed of 50RPM with an S21 Spindle, the samples maintained at 25 ° C using a thermoregulated water bath.

Typically, the curing agent is added in an appropriate amount. By "suitable amount" is meant a quantity that may be considered appropriate by those skilled in the art depending on the type of hardening accelerating agent. Typically, in the case of triacetin, an appropriate amount is for example between 3 and 20% by weight of triacetin, preferably between 4 and 17%, more preferably between 5 and 15%, more preferably between 6 and 10% or between 6 and 8%, typically about 7% by weight.

The invention also relates to the use of a composition according to the invention, for the preparation of particle boards or fibers.

By "particle board or fiber board" is meant panels composed of particles or fibers, more particularly fibers of vegetable origin. Particle boards are, for example, products composed of particles or chips, obtained by cutting wood on specialized machines (cutters, hammer mills). The particle boards are defined by the NF EN 309 standard and their requirements are specified by the NF EN 312 standard. Typically, the particles may have sizes of between 1 mm and 10 cm. For example, particles up to 10cm are found in Oriented Strand Board (Oriented Strand Board) panels that can be obtained by using the composition according to the invention. Fibreboard is composed of lignocellulosic fibers such as wood fiber, flax or hemp, kenaf, sisal, jute, ramie, nettle, bamboo fiber or viscose fiber. Such fiber boards are for example defined by the European standard NF EN 316 and their characteristics are specified by European standards NF EN 622-1 to 622-5.

The particle board is prepared by mixing wood particles or chopped wood fibers with the adhesive composition according to the invention, and curing the composition under pressure and at elevated temperatures. Thus, the resin dose may vary between 6 and 12% by dry weight of the wood particles or fibers used. In general, values between 8 and 10% are used.

The invention is applicable to any type of particles or fibers, in particular of plant origin such as wood particles (large chips, particles, shavings, sawdust) and / or other lignocellulosic material in the form of particles (shives). hemp, flax shives, bagasse fragments)

The particle board material thus obtained was tested for its mechanical properties and clearly showed the influence of the addition of triacetin on a a number of properties such as swelling, internal cohesion, modulus of elasticity and formaldehyde emission. In addition, the addition of triacetin also results in a reduction in the maximum polymerization temperature.

The invention also relates to the use of a composition according to the invention, for the preparation of rigid phenolic foams or particle or fiber boards, in particular panels of particles or plant fibers and in particular lignocellulosic fibers.

By "rigid phenolic foams" is meant mosses in particular as defined according to ISO 4898 of 2010 in its additive No. 1 of 1988 (also formerly the French standard NF T 56-204). Such foams are obtained from liquid resins. The exothermic crosslinking of the phenol resin causes the vaporization of a blowing agent and the formation of a high proportion of closed cell foam. Such foams are used in thermal insulation, particularly in the form of panels.

The invention also relates to the use of a vegetable protein hydrolyzate and more particularly wheat protein in the replacement or reduction of formaldehyde in phenolic resin compositions. Especially in formaldehyde-based resins, such as urea formaldehyde resins (UF-resins), melamine-urea-formaldehyde (MUF-resins) and Phenol-formaldehyde (PF-resins). Typically, 10 to 25 mol% of the phenol of the phenolic resin is substituted with a plant protein hydrolyzate Γ vegetable protein hydrolyzate preferentially so that the phenol: aldehyde molar ratio is from 1: 1.5 to 1: 1.7 .

Finally, the invention relates to a rigid phenolic foam board or a particle board or fibers preferably reduced formaldehyde content comprising the composition according to the invention. Hereinafter, the invention will be illustrated by a number of examples relating to the preparation of resins and their use as binder in the preparation of particle board compositions. These examples can in no way be interpreted as limiting the scope of the invention or the patent rights claimed in the claims. Example 1 Preparation of a Phenolic Resin Containing a Protein Hydrolyzate

In a 500 ml glass reaction vessel, 105.75 g of (0.9 mole), a solution of 80% phenol 50 ml 30% NaOH (0.35 moles) and a 37% formaldehyde solution 100 ml (1.2 moles) are mixed together for 30 minutes at 30 ° C. Then 1.75 g of wheat protein hydrolyzate is added so that the reaction mixture is heated slowly to 94 ° C then maintained at this temperature for about 30 minutes. Then, an additional amount of formaldehyde is added which corresponds to 0.5 mol. The reaction is then continued until a viscosity is reached between 0.5 and 0.8 Pa.s at 25 ° C. The final pH should be around 1 l.

The resin thus obtained contains 10% of a protein hydrolyzate. In order to increase the protein content by 20%, the phenol portion is reduced to 94 g (0.8 mole) and the protein portion is increased by 1.75 g.

Three types of hydrolysates of wheat proteins are used:

• SOLPRO® 508 (product marketed by TEREOS SYRAL): an enzymatic hydrolyzate of wheat gluten;

· SOLPRO® 050 (product marketed by TEREOS SYRAL): an acid hydrolyzate of wheat gluten;

• A low molecular weight wheat protein hydrolyzate (LMW) experimental product having an average molecular weight of about 6000 Da. By a preliminary study, the inventors have demonstrated that triacetin is more suitable in accelerating the hardening of phenolic compositions. comprising a hydrolyzate of vegetable proteins since it confers a good acceleration of the hardening for a stability of the hardening mixture allowing an industrial use of the composition obtained, this with small amounts. Thus, triacetin showed a mixture stability of up to 5 hours for a triacetin amount of 5 to 10% of the dry substance of the resin. Comparative tests have been made in particular with esters such as propylene carbonate or methyl formate.

The resins prepared in the following examples were used as such or combined with triacetin (7% of the dry substance of the resin).

Example 2 Preparation of particle boards

Particle boards are prepared using the phenolic resins obtained by the method described in Example 1. The resins used are shown in Table 1:

Table 1

Particle board is prepared by mixing 100 g of wood particles (2.5% moisture content) with 10 g of resin solids. The resin as such has a moisture content of about 50 to 55%. A series of panels is prepared without addition of triacetin, a second series with an addition of 7% of the dry substance of the resin (here 0.7 g). The mixtures are then pressed into a mold to obtain panels. The mold has the following dimensions: 14x300x350 mm. The treatment conditions are as follows: heating at 160 ° C while pressing three consecutive and decreasing pressures. This is shown in Table 2:

Table 2

Example 3: Swelling behavior of the prepared panels: In this example the swelling behavior was tested on panels made with the resins prepared in Example 1. The panels tested have a thickness of 13 mm. The swelling behavior is thus determined as described in standard NF B51-262. First the thickness of the panel is measured and then the panel is baked for 2 hours. After cooking, the panels are oven-dried at 103 ° C. for 24 hours.

The dry swelling value G is then determined as follows:

G (%) = dry thickness after swelling - dry thickness before swelling x 100

Dry thickness before swelling

The effect of the addition of triacetin to phenolic resins containing the protein hydrolyzate is clearly demonstrated in Table 3, which displays much lower swelling values than without triacetin.

G (%) without triacetin G (%) with triacetin

Reference 9.9 7.8 IR 21.9 5.4

R2 10.7 6.2

R3 1 1.7 5.5

Table 3: swelling behavior of the resin-based panels of Table 1.

Example 4: internal cohesion of the panels: In this example, the internal cohesion before swelling (according to EN319) and after swelling (according to EN321) is determined. The values are expressed in N / mm ² in Table 4. These values again show the effect of the presence of triacetin on phenolic compositions containing proteins.

Table 4: Effect of Presence of Triacetin on Phenolic Compositions Containing Proteins

Example 5: Formaldehyde emission of particle boards:

To be classified as class E1, the formaldehyde emission of the panels must be less than 6.5 mg / 100g on dry panel, according to EN312, as determined by the method described in EN717-3. In Table 5 below, the formaldehyde emissions of panels made with adhesives according to the invention are presented. Resins cont. 7% triacetin Emission formaldehyde (mg / 100g)

Reference 3,88

RI 3.74

R2 4.62

R3 2.1 1

Table 5: Formaldehyde emissions

The inventors have observed that compared to the panels which do not comprise gluten hydrolyzate, the panels comprising a gluten hydrolyzate showed a lightening of the panel visible to the naked eye. This characteristic of the panels obtained by the use of the compositions according to the invention makes it possible, for example, to reduce the thickness of the coating required to obtain color panels and in particular white panels. Such thinning is particularly advantageous in the main use of these panels in the building field.

Claims

Composition based on phenolic resin, characterized in that it comprises at least one phenolic resin, a hydrolyzate of plant proteins, preferably a hydrolyzate of wheat gluten, and a curing accelerating agent.

Composition according to Claim 1, characterized in that 10 to 25 mol% of the phenol of said phenolic resin is substituted with a hydrolyzate of vegetable proteins, and in that the molar ratio of phenol: aldehyde is 1: 1.5 to 1 : 1.7.

Composition according to either of Claims 1 and 2, characterized in that the hardening accelerating agent is chosen from triacetin, butyrolactone, caprolactone and propylene carbonate.

Composition according to any one of the preceding claims, characterized in that the content of the agent accelerating the hardening is between 4 and 10% by weight of the resin solids, preferably between 6 and 8%.

Composition according to any one of the preceding claims, characterized in that the hydrolyzate of wheat gluten is obtained by acid or enzymatic hydrolysis.

Composition according to any of the preceding claims, characterized in that the hydrolyzate of wheat gluten is obtained by enzymatic hydrolysis and has an average molecular mass of between 3 and 20 kDa, preferably between 4 and 15 kDa.

Composition according to any one of the preceding claims, characterized in that the hydrolyzate of wheat gluten is additionally deamidated. Process for forming a phenolic resin composition typically, a wood glue type adhesive composition characterized in that the process comprises the following steps:

heating the resulting mixture to a temperature of 90-98 ° C and maintaining at that temperature for about 15 minutes to one hour; add additional formaldehyde to give a phenol: formaldehyde ratio of 1: 1.5 to 1: 1.7;

mixing the resin obtained a curing accelerating agent.

9. Use of a composition according to any one of claims 1 to 7, for the preparation of rigid phenolic foams or particle board or fiber, particularly particle boards or plant fibers.

10. Use of a hydrolyzate of vegetable proteins and more particularly of wheat proteins in the replacement or reduction of formaldehyde in phenolic resin compositions.

Rigid phenolic foam board comprising a composition according to any one of claims 1 to 7.

A particle or fiberboard comprising a composition according to any one of claims 1 to 7.