DD221461B1 - PROCESS FOR BINDER PRODUCTION FOR THE MODIFICATION OF COATINGS - Google Patents

Description

Characteristic of the known technical solutions

The use of carboxy group-containing elastlatices in coating compositions based on aqueous polymer dispersions for the corrosion protection of metals is known and is u.a. in DD-PS 202297 described. However, it has been known for several years that the blasting of concrete elements is not caused in the first place by leaching, base exchange, crystallization or blooming, but by undercutting.

Corrosion is the inadvertent destruction of materials. Sometimes, the destruction of one material may result in the destruction of another, even though this material alone would not have corroded. This can be z. B. happen on concrete elements with metal reinforcement. The rusting of the metal within the concrete elements leads to the demolition of the concrete and ultimately to a gradual complete destruction of the element. Especially for concrete elements that are used in the housing sector, this results in large economic losses and hazards.

The corrosion behavior of the reinforcement is determined not only by the position of the metal used in the electrochemical series, but also by the presence of foreign substances or admixtures in the metals and by the composition of the building material. Since the corrosion of high polymer materials is relatively insignificant due to their high chemical resistance, it is obvious that this property u.a. also used for the corrosion protection of metals.

According to Brockhaus ABC Chemistry, Volume 1A-K, VEB F.A. Brockhausverlag Leipzig, 1971, page 724, corrosion protection by coatings as the separating layer between metal and corrosive agent is the most common. The problem here is always the nature of the surface of the metal, which in principle requires careful preparation of the surface. However, z. B. by welds on the metal surface to be treated, a different adhesion or adhesion of the molecules occur at the interfaces.

In DD-PS 129662 coating compositions of combinations of synthetic latexes with functional groups and conventional known starting materials are described. The usual used agents such as inorganic pigments, softeners, etc., usually react destabilizing to temperature increases or call by a slow;

Salt concentration increase a phase separation. The corrosion protection coatings according to DD-PS 129662 and 146613 with their main advantages and disadvantages, but are only suitable for corrosion protection of metal surfaces that are not enclosed, such. B. of metal reinforcements in concrete elements, but z. B. for car underbody protection. The destruction of components with metal reinforcements, such. As braids or fabrics or Baublechen is counteracted by protective coatings; one speaks of protective procedures. Such protective coatings usually consist of tar or pitch. To improve the adhesion, the solvents originally used are increasingly being replaced by aqueous emulsions, since not only the economic advantages but also the environmental pollution is reduced. Furthermore, a significant advantage is that aqueous dispersions or emulsions can be applied to wet substrates, which is not possible with solvent-containing products.

For protective coatings, a distinction depending on the feed different tars, such. As hard coal, lignite, wood, bone and fats. On an international scale, only hard coal or Used oil or lignite coal tar. During production, several compounds are formed, some of which are still contained in the tar. For example, coal tar contains predominantly aromatic compounds and brown coal tar predominantly aliphatic hydrocarbons. For several reasons binders based on high polymer are added to the protective compositions. This will u.a. improves the adhesion, but also enhances the film texture by impermeability. For stability reasons, a compatibility of all components is necessary, since otherwise the unstable materials precipitate quickly and / or also form uneven protective films. Normal aqueous emulsion polymers are therefore unsuitable because the adhesion is insufficient, the high emulsifier content adversely affects the water resistance and there is no resistance to the compounds contained in the tar.

It is furthermore known that the quality of the latex particles can be influenced by a controlled use of emulsifier. Thus, according to Houben-Weyl Volume 14/1 p.337-339 by staggering the emulsifier addition, targeted use of

low emulsifier, latex particles between 2000 and 3500 angstroms available. But these latices are not useful as binders for protective compounds because they are unstable and their strength and film properties do not meet the desired requirements.

The great importance of brown coal coking according to the brown coal high temperature method (BHT) for our economy automatically means that the supply of BHT tar and pitch will increase. The latter, however, contain compounds which have a corrosive effect on metals and also destabilizing known binders. In particular, phenols and creosote are mentioned here, including nitrogen compounds in the form of pyridine bases and sulfur-containing body, especially Thiophenhomologe.

Object of the invention

The aim of the invention is to produce a binder which in combination with mixtures of bitumen, tar or pitch, in particular those from the BHT coking, with or without other additives for coating compositions with improved properties with respect to heel formation, adhesion to iron and / or steel and increased film strength is suitable.

Explanation of the essence of the invention

The invention has for its object to develop a manufacturing method for a binder for modifying coating compositions, which meets the above requirements.

The object is achieved in that dienes having 4 to 8 carbon atoms, for. B. butadiene-1,3, with conjugated ethylenically unsaturated carboxylic acids and 56 to 60% styrene or ring-substituted styrenes in the presence of at most 0.5% emulsifier in aqueous emulsion in 3 temperature stages are polymerized as follows:

20% of the monomers are at temperatures below 65 ° C,

70% of the monomers between 65 and 80 ° C and

the rest of the monomers over 8O ⁰ C almost completely

implemented such that a latex having an average particle size of greater than 2000 angstroms is formed.

As conjugated dienes are those having 4 to 8 carbon atoms, in particular a diene having 4 to 6 carbon atoms, preferably 1,3-butadiene used. When it has an alkyl substituent, the alkyl group contains 1 to 2 carbon atoms. Preferably, this is the methyl group. Examples of suitable alkyl-substituted butadienes are isoprene, piperylene and 2,3-dimethylbutadiene-1,3, with isoprene being preferred.

The ethylenically unsaturated carboxylic acid compounds which can be used according to the invention include: acrylic acid, methacrylic acid, crotonic acid, itaconic acid and fumaric acid.

According to the invention, known anionogenic emulsifiers, such as alkylarylsulfonates, sulfated esters of fatty acids, sodium laurylsulfate can be used individually or in a mixture. Such emulsifiers are also well tolerated with nonionic emulsifiers such as Alkylphenolpolyäthoxyläthanolen or other Polyglykoläthern that arise in the reaction of 3 to 30 moles of ethylene oxide with fatty alcohols having 10 to 20 carbon atoms and are often included as a dispersant in pigments or other dispersions and so in get a coating mass.

Suitable polymerization initiators are the customary polymerization catalysts for emulsion polymerizations, in particular water-soluble peroxidic catalysts, such as ammonium sulfate, potassium persulfate, and hydrogen peroxide.

In addition, water-soluble azo compounds which decompose in aqueous solution at temperatures between 50 and 100 ⁰ C with radical formation, such as azodiisobutyronitrile and diisobuttersäurediamid be used. Mixtures of catalysts of the type mentioned and mixtures of catalysts of the type mentioned with non-water-soluble catalysts such as benzene peroxide or cumene hydroperoxide are possible.

It should also be noted that when using regulators only sulfur-free controller are suitable. Sulfur appears to have a negative influence on the adhesion of the coating to metals. This is also the basis of one of the causes of property improvements of the inventive carboxyl-containing polymers, since no sulfur is necessary for their crosslinking, as in conventional butadiene / styrene latexes without functional groups.

The invention will be explained below by way of examples. The stated parts and percentages are by weight, example 1 being according to the invention and example 2 indicating the state of the art.

embodiments example 1

In a stirred autoclave 552Tl. Distillate, 8 parts Potassium persulfate, 2.1 TI. Sodium benzenesulfonate, 4,5Tl. a mixture of fumaric and acrylic acid, 5Tl. Sodium hydrogencarbonate, 6Tl. Carbon tetrachloride, 59Tl. Styren and 39Tl. Butadiene, 3 hours below 65 ⁰ C react, then about 380Tl. a mixture consisting of 293Tl. Styrene and 210Tl. Butadiene between 65 and 8O ⁰ C reacted, after which the remaining amount of the mixture is further reacted at a temperature of about 80 ⁰ C to a nearly 100% conversion of all monomers. At the end of the reaction, the pH is adjusted to 7.5.

Example 2

In a stirred autoclave 552Tl. Distillate, 8 parts Potassium persulfate, 1.7Tl. Sodium benzenesulfonate and 0.3 part. Alkylphenolpolyethoxyglycol with an HLB value of 12,4,4,5Tl. a mixture of fumaric and acrylic acid, 4,3Tl. Sodium hydrogencarbonate, 6Tl. Carbon tetrachloride, 59Tl. Styren and 39Tl. Butadiene is reacted for 3 hours at a temperature below 65 ° C, then about 380Tl. a mixture consisting of 293T1. Styrene and 210Tl butadiene between 65 and 8O ⁰ C reacted, after which the remaining amount of the mixture is further reacted at a temperature of about 8O ⁰ C to a nearly 100% conversion of all monomers. At the end of the reaction, the pH is adjusted to 7.5.

Example 3

In a stirred autoclave 544Tl. Distillate, 7,6Tl. Potassium persulfate, 0.8Tl. Sodium lauryl sulfate, 0.5Tl. a fatty alcohol (C ₁₂ -C ₁₈ ) with about 7 moles of AO, 1,9Tl. Acrylic acid, 0.9 part. Methacrylic acid, 1.7Tl. Fumaric acid, 3,6Tl. Sodium hydrogencarbonate, 6Tl. Carbon tetrachloride, 55Tl. Styren and 43Tl. Butadiene 2.5 hours at 60-62 ⁰ C reacted, then about 360Tl. a mixture consisting of 290Tl. Styren and 212Tl. Butadiene at 72 to 75 ⁰ C reacted, after which the remaining amount of the mixture is further reacted at a temperature of 85-86 ° C to close to 100% conversion of all monomers. At the end of the reaction, the pH is adjusted to 7.5.

Example 4

According to a conventional emulsion polymerization method of addition, a carboxylated latex was prepared using the same amounts of raw materials as used in Example 1, according to the current state of the art.

Example 5

For further comparison, a commercial rubber latex with about 51% styrene and 49% butadiene was used. Table 1 shows some physical characteristics.

Table 1

1 50.8 2 50.7 example 50.7 4 50.4 5 51.2 2180 2 470 3 3 560 1640 800 Gesamtfeststoffin% 45 42 42 55 40 0 particle size in angstroms 7.5 7.5 7.5 7.5 10.5 Surface tension dyne / cm) PH value 6.5 6.7 6.6 6.5 4.5 Filmfestigk. in (N / mm ² ): 13.0 13.4 12.8 11.5 7.5 after 24 hours at 20 ⁰ C after 10 min at 120 ⁰ C.

Example 6 to 10

20TL. Latex of Examples 1 to 5 were mixed with a BHT-Teerdispersion consisting of 55Tl. a 6% alkaline

Casein solution and 45Tl. BHT tar, mixed.

In Table 2, the values for the formation of sediment according to Wassmuth-Boiles are given, whereby the force is measured in g, which is necessary to push a cone with certain dimensions through the sedimented layer to the ground. 10g mean a still very easy to touch sediment, 300g a hard, no longer touchable

Sediment.

Table 2 example

with latex

Sediment in g after 1 3

14

90 days

6 1 7 2 8th 3 9 4 10 5

10 10 10 10 10 20 180 10 10 10 10 10 25 200 10 10 10 10 10 40 250 10 10 30 80 200 300 - 10 20 50 100 300

Further, 25 g of the mixtures of Examples 6-10 was placed on an iron plate of 50 χ 100 mm, placed on a same plate and dried under the same slight pressure of 0.1 N / mm ^{2 for} 2 hours at 7O ⁰ C.

Table 3 shows the force required to separate the 2 iron plates. It thus gives a comparison to the metal adhesion of the various mixtures.

Table 3

Examples 6 7 8th 9 10 applied force (N / mm ² ) 1.8 1.9 1.3 0.7 0.15

Claims (1)

A process for the preparation of binders for the modification of coating compositions of bitumen, tar or pitch or their mixtures by copolymerization of conjugated dienes having 4 to 6 carbon atoms, 56 to 60% styrene or ring-substituted styrene and ethylenically unsaturated carboxylic acids in the presence of at most 0.5% emulsifier in aqueous emulsion and in conducting the polymerization in three temperature stages, wherein 20% of the monomers below 65 ° C, 70% between 65 ⁰ C and 80 ⁰ C and the rest of the monomers above 80 ⁰ C to a nearly complete reaction, characterized characterized in that the average particle size is carried out to a value above 2000 angstroms. Field of application of the invention The invention relates to a process for the preparation of binders for the modification of coating compositions based on a carboxylated copolymer latex. By the method of preparation according to the invention an improved intermolecular interaction between this binder and bitumen, tar or pitch or their mixtures is effected.