WO2006018134A1 - Wetting agent for impregnating resins - Google Patents

Abstract

The invention relates to an impregnating resin comprised of melamine formaldehyde resins that, as wetting agents, comprises one or more glycol ethers of the following structural formula RO(C2H4O)nH, in which R represents branched C5 to C15 alkyl and n ranges from 2 to 10. The invention also relates to the use of the glycol ethers as a wetting agent for impregnating resins.

Description

Wetting agent for impregnating resins

description

The invention relates to a impregnating resin of melamine-formaldehyde resins, which as Netz¬ medium one or more glycol ethers of the following structural formula

RO (C ₂ H ₂ O) _n H

contains, where

R = branched C ₅ - to C ₅ alkyl and n = 2 to 10;

and the use of glycol ethers as wetting agents for impregnating resins.

In the impregnation of papers, for example with impregnating resins, nonionic surfactants are used as auxiliaries. These have a positive effect on the wetting behavior of the resin particles, in that they accelerate the rapid and uniform diffusion of the resin particles into the fibers by lowering the surface tension.

A disadvantage of the use of surfactants is the foaming which occurs, for example, has a time-inhibiting effect on the impregnation process. The operating speed of the impregnating machine must be adapted to the foam development of the particular surfactant.

As wetting agents for impregnating resins, ethoxylated fatty alcohols and alkylphenol ethoxylates used in an amount of from 0.2 to 0.6% by weight, based on the resin solution, are used in the prior art (for example DE-A 41 17 841 and DE-A 199 54 189).

It has long been known, however, that alkylphenol ethoxylates are difficult to biodegrade and are aquatoxic, and have potential endocrine activity. In animal experiments, as a consequence of the action of alkylphenol ethoxylates infertility and malformations as well as cancer on reproductive organs could be detected.

On the basis of these findings, the use of the alkylphenol ethoxylates in their main application areas, such as, for example, in the personal care and laundry industry, has been discontinued. However, in smaller industries in which the Alkylphenolethoxy¬ late are used only as an aid, these are still of importance today. The object of the present invention was therefore to find environmentally friendlier auxiliaries for aminoplast resins which have comparable qualities to the alkylphenol ethoxylates. Furthermore, the object was to show wetting agent for impregnating resins, when used in comparison to the prior art, a reduced foaming, in particular no foaming occurs.

Surprisingly, it has been found that impregnating resins made from melamine-formaldehyde resins which, as wetting agents, comprise one or more glycol ethers of the following structural formula

RO (C ₂ H ₄ O) _n H

contain, where

R = branched C ₅ - to C ₁₅ -alkyl and n = 2 to 10,

particularly suitable for the production of aminoplast resin films and films for coating wood-based materials.

The impregnating resins according to the invention are readily biodegradable and have no aquatoxicity and no endocrine activity.

Advantageously, the wetting agents used are glycol ethers having a center of gravity at n = 4 to 8, in particular at a center of gravity at n = 6. In the case of the numerical indication of the ethoxy units, the mean value of the ethoxy unit distribution is specified as the center of gravity. These are generally broad distributions, so that with a center of gravity of n = 6, some molecules may even exist with n = 2 or 3 and others with n = 12 or 13.

The radical R is a branched C ₅ - to C ₁₅ -alkyl, ie a branched saturated hydrocarbon having 5 to 15 carbon atoms.

For example, the radical R is a branched propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, 2-methylpentyl, heptyl, 2-propylheptyl, octyl, 2-ethylhexyl , Isooctyl, nonyl, isononyl, decyl, isodecyl, undecyl, dodecyl, tridecyl, isotridecyl or tetradecyl, where the alkyl chain can each be branched at any position. (The above designations isooctyl, isononyl, isodecyl and isotridecyl are trivial terms and are derived from the alcohols obtained by the oxo process - see Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, Vol. A 1, pages 290 to 293, and Vol , Pages 284 and Simple or multiple branches are possible. The respective branches preferably consist of C _m H _{2m +} r groups with m greater than or equal to 2.

The radical R is advantageously a branched C ₈ - to C ₁₂ -alkyl.

In particular, the radical R is a

- C ₆ - to C ₁₀ -alkyl branched with 1 C ₂ H ₅ group;

- C ₅ - to C ₉ -alkyl branched with 1 C ₃ H ₇ -group; - C ₄ - to C ₈ -alkyl branched with 2 C ₂ H ₅ groups or 1 C ₄ H ₉ group;

- with 1 C ₂ H ₅ group and 1 C ₃ H ₇ group or with C ₅ H ₁ - _I -GrUpPe branched C ₄ - to Cy-alkyl;

- with 3 C ₂ H ₅ groups or 2 C ₃ H ₇ groups or 1 C ₂ H ₅ group and 1 C ₄ H ₉ - group branched C ₄ - to C ₆ -AIRyI; with 2 C ₂ H ₅ groups and 1 C ₃ H ₇ group or 1 C ₃ H ₇ group and 1 C ₄ H ₉

Group branched C ₄ - to C ₅ -alkyl;

- C ₄ -alkyl branched with 4 C ₂ H ₅ groups or 1 C ₂ H ₅ group and 2 C ₃ H ₇ groups;

where n = 6 is particularly preferred.

The radical R is particularly preferably a mono- or propyl-branched nonyl, octyl, heptyl or hexyl.

Very particularly preferably, the branching consists of a C ₃ H ₇ group, in particular the radical R is 2-propyl heptyl and advantageously n = 6.

In the suitability of a molecule as an adjuvant, the ratio of hydrophobic (residue R) to hydrophilic groups (ethoxy groups) is a crucial factor. Thus, a comparable effect on the wetting behavior of the resin particles is to be expected if molecules are used whose ratio of hydrophobic to hydrophilic molecule content corresponds to that of the glycol ethers used according to the invention, but their respective hydrophobic and hydrophilic molecular structure is twice (eg with R = C ₂₀ alkyl and n = 12) or three times (for example with R = C ₃₀ alkyl and n = 18) is as large as that of the glycol ethers used in the invention. This comparable effect is expected only up to a certain molecular size, since too large molecules make it difficult to diffuse quickly.

As a wetting agent it is also possible to use a mixture of the glycol ethers used according to the invention and alcohols known in the prior art. The mixing ratio of glycol ethers to alcohol is usually 90:10 to 30:70, especially 80:20 to 40:60. As alcohols can advantageously C ₇ - to C ₁₂ - alkyl alcohols are used, which are preferably linear or optionally methyl-branched. However, the use of glycol ethers exclusively used according to the invention as wetting agents is preferred.

The wetting agent is usually used in an amount of 0.05 to 1% by weight, based on the resin solution, i. Impregnating liquor, used. Preferably, an amount of 0.1 to 0.7 wt .-%, in particular 0.2 to 0.5 wt .-%, is used.

In the resin solution, the aminoplast resin is usually present at 40 to 70 wt .-%, in particular from 50 to 60 wt .-%. Suitable crosslinkable aminoplastic resins are all resins known to the person skilled in the art, in particular melamine-urea-formaldehyde and melamine-formaldehyde resins or mixtures thereof. These resins may be partially or completely etherified with alcohols, preferably C ₁ -C ₄ -alcohols, in particular methanol or ethanol. Preference is given to using etherified and unetherified melamine-urea-formaldehyde and melamine-formaldehyde resins or mixtures thereof, in particular etherified and unetherified melamine-formaldehyde resins.

The impregnating resin according to the invention may be admixed with auxiliaries and additives known to the person skilled in the art, for example urea, caprolactam, phenyldiglycol, butanediol, saccarose, as well as curing agents and catalysts.

The manner in which the impregnating liquor is further processed into melamine resin impregnates and how the coating of the wood-based materials takes place with these impregnates is known to the person skilled in the art.

The impregnating resins according to the invention are therefore advantageously further processed into aminoplast resin films or films for the coating of wood-based materials.

The inventive impregnating resins are characterized by good adhesion, improved gloss, high degree of blackening and low cracking. The foaming could be significantly reduced compared to the prior art.

The invention further relates to the use of glycol ethers of the following structural formula

RO (C ₂ H ₄ O) _n H,

in which

R = branched C ₅ - to C ₁₅ - alkyl n = 2 to 10, as a wetting agent for amino resins, in particular impregnating resins. Example:

Table 1: Wetting agent

*) according to the invention

100 parts of a commercially available melamine-formaldehyde impregnating resin with a ratio of melamine to formaldehyde of about 1: 1, 6 and a solids content of about 60% were mixed with 7.1 parts of water, with 0.3 parts of hardener (for example SO ₂ buffered amines) and mixed with 0.3 part of wetting agent (Examples 1 to 4).

The turbidity time was 305 seconds for all impregnating resins. In each case, a white and a black decorative paper were impregnated with the five different impregnating resins according to DE 199 54 189.

Table 2: Impregnating liquor

The decorative paper was pressed onto an HDF plate at 190 ^° C. and 20 kp for 35 minutes. The data of the surface evaluation are shown in Table 3. Table 3: Surface evaluation

Requirements for the performance test:

hardening

The quality of the cure is determined by exposing the coated chipboard to a 0.2N hydrochloric acid stained with 0.004 wt.% Rhodamine B solution for 16 hours. With good curing, the surface is not attacked by the acid. The strength of the attack can be judged by the strength of the red color.

Evaluation:

0 = no attack 1 = weak pink color

2 = distinct red color

3 = strong red color

4 = strong red color with slight surface swelling

5 = strong red coloration with strong surface swelling 6 = destroyed surface.

shine

The gloss measurement is carried out according to DIN 67 580 by reflection measurement of a light beam at an angle of incidence of 20 °. The gloss is the better, the higher the proportion of the reflected light given in%.

unity

The closed nature or porosity of the coated chipboard surface serves to assess the sensitivity to dirt. The surface to be tested is rubbed in with black shoe polish and then cleaned again with a cloth. The shoe polish remaining in the pores allows an assessment of the closeness of the surfaces.

The assessment of the surface closure is carried out in the following stages: 0 = free of pores

1 = isolated pores

2 = few pores

3 = frequent pores 4 = many open spots

5 = a lot of vacancies

6 = no closure.

crack resistance

The crack resistance of a surface is determined according to DIN 53 799. The beschich¬ preparing particle board is h over a period of 24 gela¬ Gert at 7O ⁰ C in a circulating air drying cabinet. Due to the drying process, shrinkage stresses occur, which lead to cracks in the surfaces. An intensification of the test can be achieved by increasing the drying temperature or by drilling the surface (notch effect). Cracking is assessed according to the following scale:

0 = no cracks

1 = isolated small cracks 2 = few cracks

3 = moderate cracks

4 = frequent cracks

5 = many cracks

6 = total cracking.

blackness

The black level measurement is carried out according to D 3265 with a Tint Tester 527 with brightness measuring head Tint Sensor. The measuring range covers 0-99.99 brightness units, where zero is the lowest brightness level (absolutely black). With values> 0.8 a clear graying is already recognizable.

After calibration of the device with a standard, the test piece is measured three times and the mean value is indicated as black level.

yellowing

In order to determine the extent of the thermal stability of the resin, the yellowing of the surface with a heatable stamp is determined under pressure. The stamp of the tester is pressed at 225 ⁰ C with 5 N / mm ² on the surface to be tested. The degree of yellowing is graded on a scale of 0-6.

Evaluation:

0 = no yellowing

1 = very slight yellowing 2 = visible discoloration

3 = moderately strong discoloration

4 = strong brown color

5 = very strong brown coloration 6 = dark brown area

To test the surface tension, the following impregnating resins were investigated:

Table 4: impregnating resins

Table 5: Surface tension

The foaming was evaluated in the preparation of the impregnating liquor with a scale of 1 to 6.

0 = no foam

1 = isolated foam, which dissolves immediately

2 = very little foaming

3 = low foaming 4 = moderate foaming

5 = strong foaming

6 = very strong foaming

Table 6: Foaming

Claims

claims 1. impregnating resin of melamine-formaldehyde resins, the wetting agent as one or more meh¬ rere glycol ethers of the following structural formula RO (C ₂ H ₄ O) _n H contains, where R = branched C ₅ - to C ₁₅ -alkyl and n = 2 to 10. 2. impregnating resin according to claim 1, wherein n = 4 to 8. 3. impregnating resin according to claim 1 or 2, wherein the radical R is a branched C ₈ - to C ₁₂ -AlkVl. 4. impregnating resin according to claims 1 to 3, wherein the respective branches consist of (C _m H _{2m +} i) -Gi ^* uppen and m is greater than or equal to 2. 5. impregnating resin according to claims 1 to 4, wherein the radical R is a branched with 1 C ₂ H ₅ group C ₆ - to C ₁₀ alkyl; 1 with C ₃ H ₇ group branched C ₅ - to C ₉ alkyl; C ₅ - to C ₈ -alkyl branched with 2 C ₂ H ₅ groups or 1 C ₄ H ₉ group; with 1 C ₂ H ₅ group and 1 C ₃ H ₇ group or with 1 C ₅ H _ir group branched C ₄ - to C ₇ alkyl; with 3 C ₂ H ₅ groups or 2 C ₃ H ₇ groups or 1 C ₂ H ₅ group and 1 C ₄ H _g group branched C ₄ - to C ₆ -alkyl; with 2 C ₂ H ₅ groups and 1 C ₃ H ₇ group or 1 C ₃ H ₇ group and 1 C ₄ H ₉ - Group branched C ₄ - to C ₅ -alkyl; - with 4 C ₂ H ₅ groups or 1 C ₂ H ₅ group and 2 C ₃ H ₇ groups branched C ₄ alkyl; is. 6. impregnating resin according to claims 1 to 5, wherein the radical R is an ethyl- or propyl-branched nonyl, octyl, heptyl or hexyl. 7. impregnating resin according to claims 1 to 6, wherein the radical R is 2-propylheptyl. 8. impregnating resin according to claims 1 to 7, wherein n = 6. 9. impregnating resin according to claims 1 to 8, in which 0.05 to 1 wt .-% wetting agent based on the impregnating resin. 10. Use of glycol ethers of the following structural formula RO (C ₂ H ₄ O) _n H, in which R = branched C ₅ - to C ₁₅ -AIRyI and n = 2 to 10 as wetting agent for impregnating resins.