FI57961B - ANALYZING AV BISULFIT- OCH / ELLER SULFIT MODIFICATIONS MELAMINE-FORMALDEHYD CONDENSATION PRODUCT SAOSOM MEDEL FOER AOSTADKOMMANDE AV FOERHOEJD VAOTSTYRKA - Google Patents

Description

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Federal Republic of Germany Förbundsrepubliken Tyskland (DE) P 2241158.1 (71) BASF Aktiengesellschaft, 6700 Ludwigshafen, Saxony Federal Republic of Förbundsrepubliken Tyskland (DE) (72) Friedrich Brunnmueller, Ludwigshafen, ne

Saxony Federal Republic of Germany (DE) (74) Oy Kolster Ab (54) Use of bisulphite and / or sulphite-modified melamine-formaldehyde condensation products as wet strength agents - Användning av bisulfit- och / eller sulphitmodifier av förhöjd vatstyrka

The invention relates to bisulphite and / or sulphite-modified melamine-formaldehyde condensation products - obtained by condensing 1 mole of meleunine or a mixture of melamine with other condensable compounds and 1.5 to 8 moles of formaldehyde or an equivalent mole of formaldehyde donating moles and and / or sulfite or an equivalent molar amount of a bisulfite donating compound - use as a wet strength agent for water-soluble binders and adhesives based on starch, its derivatives and reflection products, proteins and polymers.

The use of wet reinforcing agents makes starch- and polymer-containing adhesives in particular very water-resistant.

Melamine formaldehyde resins modified with bisulphite and / or sulphite form a long-known group of high molecular weight condensation products which have hitherto been used, for example, as sizing agents in the paper industry (cf. DE 873 652) and which are also particularly formulated to increase the wet strength of papers containing paper (cf. U.S. Patent No. 2,863,8 ^ 2).

The problem of such excipients consists of the following:

It has long been known that melamine formaldehyde resins, which are themselves insoluble in water, can be used as bulk reinforcing agents.

However, their use, especially in aqueous systems, always becomes difficult because these substances are insoluble in water and can therefore only be difficult to distribute evenly throughout the reaction space. In other words, according to these moisture-resistant resins, the performance of emulsification has so far been almost impossible. Sulfite modification and generally modification with other compounds that solubilize condensation resins, such as amidosulfonic acid, etc., is also known, but has been used only to the extent that 0.2 mol of bisulfite was added to 1 mole of melamine for a particular wet strength purpose (cf. patent publication 2 870 0U1). Until now, it has been thought that too many water-solubilizing groups in a condensing resin destroy the properties that provide wet strength, because these solubilizing groups at least cause the resin to swell again.

The bisulfite and / or sulfite-modified excipient based on melamine formaldebyde resins used according to the invention mixes easily with the aqueous system formed by binders or adhesives, so that it is easy to handle.

According to the invention, in particular adhesives and glues based on starch, their derivatives, disintegration products, proteins and certain polymers, which swell very easily in water and have long been used as adhesives and binders, are treated so that they can be washed with water for long periods of time without being damaged.

The preparation of the substances to be used according to the invention is simple and takes place in such a way that, in the pH range from 7 to 12, preferably in the range from 7.5 to 8.5, the reactants are mixed and heated, the degree of condensation being selected for each application.

Particularly effective products are obtained when 2.5 to 5 molar parts of formaldehyde or formaldehyde-donating compounds and 0.3 to 0.7 molar parts of bisulfite and / or sulphite or bisulphite-donating compounds are added to 1 molar part of melamine in the corresponding molar ratios.

Other condensable compounds, such as urea, dicyandiamide, amines, acid amides, phenol or resorcinol, can also be used together with melamine, in which case the amount of the mixture is one mole. Etherified melamine can also be used, in which case the alcohol may be a saturated alcohol having 1 to 5 carbon atoms, such as methanol or ethanol.

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Formaldehyde is suitably used in aqueous solutions of formaldehyde (formaldehyde content 30%), in particular a commercial formalin solution. Suitable formaldehyde-donating compounds are the polymerization and condensation products of formaldehyde, such as paraformaldehyde or urotropin, as well as formaldehyde disulfide derivatives. Also suitable are cleavable methylol compounds, such as strongly methylated melamine, in which case its dosage must be adjusted to the stated molar limits.

As the bisulfite and / or sulfite, water-soluble alkali bisulfite or alkali sulfite is suitably used, preferably as the sodium salt.

If mixtures of alkali bisulfite and sulfite are used, the ratio of alkali bisulfite to sulfite is about 1: 0.1+.

As a bisulfite donor, a by-product of formaldehyde and bisulfite in particular is suitable. When this by-product is used, - a molar ratio of formaldehyde to bisulphite of 1: 1 is formed.

In this case, the molar ratio of free formaldehyde is adjustable within the above limits.

In condensation, it is possible to select degrees of condensation which differ greatly in the viscosities which make them up, since adhesives and binders inherently have so many different uses that it is necessary to choose different degrees of condensation. In general, it can be said that a higher degree of condensation achieves a more favorable storage stability for melamine formaldehyde resin than a lower degree of condensation, which, however, also achieves a sufficient storage stability.

Sulfites or bisulfites may be added to the condensation reaction at an arbitrary stage. They can even be added after the main condensation of melamine or melamine mixtures with formaldehyde. In this case, however, it is necessary to post-condense for some time.

A particularly preferred procedure for preparing sulfite-modified melamine formaldehyde resins is, for example, the following: As a + 0% aqueous solution, is heated to T0-100 ° C, where it is maintained during the next condensation step, and the pH of the solution, which is already at about 90 ° C from 9 to 11, drops to about 8 after a short time. 0-8.2 The addition of an alkaline reactant such as sodium hydroxide maintains the pH at 8.0-8.2 1 1/2 -2 1/2 hours, then allows the pH to lower automatically and condensation is continued. until the viscosity of the 30% solution at 20 ° C is 90-150 mPa.s.The solution is then cooled to room temperature and the solids content of 11 57961 is adjusted to $ 30-50 with water. at the end of the denaturation was about 7 "to 7.5, adjusted with sodium hydroxide or other similar alkaline reactant to a value of about 9-10.

Said viscosities can vary over a wide range and, as mentioned above, cannot be unambiguously determined due to the different uses. If the above viscosities are chosen, then an excipient is formed mainly for adhesives based on starch, dextrin, carboxymethyl starch, casein and polyvinyl alcohol.

Surprisingly, the new materials, even in amounts of 0.5% by weight, based on the solids content, give the wet material excellent properties.

The new substances can be used when it is desired to produce materials which swell or are soluble in water, i.e. binders and adhesives based mainly on starch, its derivatives such as carboxymethyl starch and its disintegration products such as dextrin, and proteinaceous binders and mixtures thereof. They can also be used in connection with plastics, when these plastics are used as adhesives or binders, as well as coatings for materials that may come into contact with water. Such plastics are prepared, for example, from polyacrylic acid, polymethacrylic acid, copolymers of acrylic or methacrylic acid with other copolymerizable compounds, such as esters of acrylic and / or methacrylic acid or amides of acrylic and / or methacrylic acid, and vinyl ethers, such as vinyl ethers, such as vinyl ethers. Polyvinyl alcohol is, for example, a plastic which can be used as a binder and an adhesive and which can be made moisture-resistant according to the invention. All these plastics usually swell or even dissolve in water. New substances can also be successfully added to mixtures of said products.

Wet strength gluing can be performed, for example, by adding about 0.5-2% by weight - based on the solid adhesive - of the condensation product used according to the invention to a commercial adhesive based on polyacrylate or dextrin, for example, and then simply drying the glued parts, possibly at elevated temperature. Thus, glued objects can be kept in water for more than 2k hours without the gluing dissolving.

The following examples illustrate the invention by means of selected manufacturing and implementation examples. The table further shows the advantage obtained over U.S. Patent No. 2,863,8U2, showing that a substantially higher amount of bisulfite significantly improves wet strength values. The table shows the wet strength in simple numbers. In this case, a value of 0 5 57961 means excellent wet strength and higher numbers always worse. It can be seen that when 0.18 moles of bisulfite per 1 mole of melamine is used, all wet strength values are in the range of 2-3, while when bisulfite is 0.22 moles or more per 1 mole of melamine, it is already below 1.

This surprising phenomenon is the basis of the present invention.

Example 1

Mixture containing 1.1+ parts by weight of a 1 + 0 # formaldehyde solution, 0.06 parts by weight of water, 0.29 parts by weight of sodium bisulfite, 0.075 parts by weight of sodium sulfite and 0.1 + 7 parts by weight part of melamine, was heated to 85-90 ° C and kept at 90 ° C during the next condensation. The pH of the solution, which was initially 10.3, dropped spontaneously to 8.0 during condensation. The pH was maintained at 8.0 for 90 minutes by the addition of dilute sodium hydroxide. The pH was then allowed to lower spontaneously and condensation was continued until the viscosity of the 50 'solution at 20 ° C was 110 mPa.s. The resulting solution was then cooled to room temperature and the solid content was adjusted to 1 + 0 # with water. The pH of the solution, which was 7.5 at the end of the condensation, was adjusted to 9.5 with 25% sodium hydroxide solution.

12.5 parts by weight of the resin solution thus obtained were mixed with 100 parts by weight of a 50% by weight dextrin solution. This mixture was used to brush a 20 x 1.5 cm strip of kraft paper at one end 2 ..... . .

3 cm area and then glued together with another soda power paper.

After 5 minutes of storage at 130 ° C, the gluing was kept in water at 20 ° C so that the gluing was subjected to a tensile stress of 200 g.

When the reference gluing made with pure dextrin glue dissolved in as little as 2 minutes and the weight dropped, the gluing performed using the resin addition remained perfect after being immersed in water for another 2k hours.

Example 2 To 100 parts by weight of a commercial 20 # starch solution was added 5 parts by weight of 1 + 0 [mu] l of the resin solution according to Example 1. Paper sheets were brushed with this mixture. After drying, the brushed sheets of paper were placed at 125 ° C for 8 minutes. A 5x5 cm piece was cut from the composed paper and placed 3 ........ .

together with 30 cm of water reagent count and stirred vigorously. When 1 drop of iodine solution was added, there was no discoloration in the aqueous solution.

In a comparative experiment using the same paper coated with a starch solution containing no resin at all under the same conditions, a deep blue color was obtained with the iodine solution.

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Example 3 200 parts by weight of a 20% cold water-soluble starch solution decomposed by mechanical and chemical treatment were mixed with 3 parts by weight of the resin solution according to Example 1. Soda kraft papers were glued with this mixture and stored overnight at room temperature. When testing wet -..... 2 ...

the strength was placed in a 3 cm glued area in water and simultaneously stressed with a tensile stress of 200 g.

After more than 2k hours of water storage, no changes in gluing were observed. The reference sizing with the same starch solution without the addition of resin decomposed when tested under the same conditions after already 20 minutes in water, at which time the weight dropped.

Example k

A mixture of 33.7 parts by weight of a 1 + 0% & formaldehyde solution, 2.65 parts by weight of water, 9.1 + 5 parts by weight of sodium hisulfite and 18.9 parts by weight of melamine was heated to 90 ° C. temperature. At 90 ° C and pH 8.5-8.0, condensation was continued until the viscosity of the 1 + 0 $ solution at 20 ° C was 100-110 mPa.s. The product obtained was then cooled to room temperature and the solids content was adjusted to 1 + 0% with water.

2 parts by weight of the obtained 1 + 0% resin solution were mixed with 300 parts by weight of a $ 5 aqueous solution of carboxymethyl starch. This mixture was glued with kraft paper, which was then kept for 2 l + hours at room temperature. Wet strength testing took place under the conditions mentioned in Example 3, i.e. A 3 cm glued area was placed in water and at the same time subjected to a tensile stress of 200 g. After immersion in water for more than 2l + hours, gluing showed no change.

The reference gluing using a 5 # solution of carboxymethyl starch without the addition of resin came off already after 3 hours in water.

Example 5 500 parts by weight of a 20 # solution of polyvinyl alcohol were mixed with 15 parts by weight of the resin solution according to Example 1. Paper sheets were glued with this mixture. The glued paper sheets were then placed in an oven at 130 ° C for 5 minutes. Wet strength testing was performed as described in Example 3.

When, in the case of comparative gluing with polyvinyl alcohol without the addition of resin, the gluing decomposed after only 11 minutes, when gluing with polyvinyl alcohol and resin, a durability of more than 72 hours in water can be achieved without change.

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Table

Molar ratio Bisulfite or Mark strength

Melamine: formaldehyde bisulphite / sulphite content (moles) a) 1: 2.5 0.15 2.0 b) 1: 2.5 0.22 0.0 c) 1: 2.5 0.33 0.0 d ) 1: 3 0.15 2.5 e) 1: 3 0.22 0.5 f) 1: 3 0.33 0.0 g) 1: h 0.12 3 h) 1: ii 0.18 2 .5 i) 1: h 0.2k 0.5 Samples a, d, g and h are resins prepared according to U.S. Patent No. 2,863,8k2. Samples were prepared according to the general instructions of Example 1 and dispensed according to Example 2. Wet strength was determined by the method described in Example 2, in which the assay values were derived from the color intensity of the iodine / starch solution (colorless = 0, deep blue = 1+).

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