DE19503284A1 - Impregnating material for mineral substrates - Google Patents

Abstract

Impregnating material contg.: (a) 100 pts. wt. NCO prepolymer with an NCO content of 2-20 wt.% and a monomeric di-isocyanate (a1) content of less than 1 wt.%, derived from: (a1 (cyclo)aliphatic di-isocyanates with a mol. wt. of 168-300, and (a2) polysiloxanes with a mol. wt. of 300-5000 contg. at least two alcoholic OH gps.; (b) 5-150 pts. wt. Si-free, 'paint polyisocyanate(s)' contg. allophanate, biuret, isocyanurate, oxadiazine, uretedione and/or urethane gps., with a (cyclo)aliphatic NCO gp. content of 10-25 wt.% and a monomeric di-isocyanate content of less than 0.5 wt.%; (c) 100-1000 pts. wt. solvent component contg. solvent(s) inert towards NCO gps.; and opt. (d) other additives etc.

Description

The invention relates to a new impregnating agent for mineral substrates Based on a special mixture of isocyanate groups applications and its use for impregnating mineral substrates.

The use of organic polyisocyanates as essential components of impregnating agents for mineral substrates is known. So describes at for example, EP-A-0 287 026 a method for protection, renovation or Restoration of stone structures by treatment with a solution aliphatic isocyanates. For its part, EP-A-0 259 644 describes impregnation medium for mineral substrates based on NCO prepolymers or semi prepolymers from (cyclo) aliphatic diisocyanates and alcoholic Polysiloxanes containing hydroxyl groups. How to the embodiments remove, is preferably in the manufacture of the prepolymers on a No removal of unreacted excess diisocyanate, obviously, so as to improve the penetration depth of the impregnating agent into the to ensure porous substrate to be impregnated.

For industrial hygiene and ecological reasons, however, is being processed tion of such impregnants containing monomeric diisocyanates high technical effort required (e.g. protective clothing, breathing apparatus u. Like.).

It was therefore the object underlying the invention, an impregnating agent to make available on the basis of monomer-free NCO prepolymers, which is the known impregnating agent based on NCO semi-prepolymers  regarding the depth of penetration, d. H. the impregnation properties and protection are at least on an equal footing, without having the ecological consequences mentioned to be partially afflicted.

This task could be accomplished with the provision of those detailed below impregnating agents according to the invention are solved. The essential to the invention Observation was that the task mentioned by using a Combination of a) a monomer-free NCO prepolymer of the following type described in more detail with b) a monomer-free lacquer polyisocyanate can be. The impregnation according to the invention based on this finding Kidney agents exhibit despite the absence of easily diffusing monomers Diisocyanates have an excellent penetration behavior and cause in particular also a reduced brittleness of the outer layers of the impregnated mineral substrates. The combinations essential to the invention from the individual components a) and b) described in more detail below not with the NCO prepolymer according to Example 1.3 of those already cited above EP-A-0 259 644 comparable because in the preparation of this NCO prepolymer the biuret polyisocyanate with a functionality above 3 together with the diisocyanate has been used to prepare the prepolymer, which at least to a lesser extent to the formation of branched By-products and a related increase in viscosity or reduced penetration depth. It was also used in manufacturing this prepolymer on the distillative removal of unreacted monomeric diisocyanate is dispensed with, so that even in this example above-mentioned occupational hygiene and ecological aspects are relevant.

The invention relates to an impregnating agent consisting essentially of

• a) 100 parts by weight of an NCO prepolymer with an NCO content of 2 to 20% by weight and a content of monomeric diisocyanate a1) of less than 1% by weight
  • a1) (Cyclo) aliphatic diisocyanates in the molecular weight range 168 to 300 and
  • a2) at least two alcoholically bound hydroxyl groups on pointing polysiloxanes of the molecular weight range 300 to 5000,
• b) 5 to 150 parts by weight of at least one silicon-free, allophanate, Biuret, isocyanurate, oxadiazine, uretdione and / or urethane groups coating polyisocyanate containing (cyclo) aliphatic bound isocyanate groups of 10 to 25 wt .-% and a content of monomeric diisocyanate of less than 0.5% by weight,
• c) 100 to 1,000 parts by weight of a solvent component consisting of at least one solvent inert to isocyanate groups,

and if necessary

• d) other auxiliaries and additives.

The invention also relates to the use of this impregnating agent for Impregnation of mineral substrates, especially concrete or Natural stone.

The impregnating agents according to the invention preferably consist of 100 Parts by weight of component a), 6 to 100 parts by weight, in particular 6 to 25 parts by weight of component b), 200 to 900 parts by weight of component c) and optionally contain auxiliaries and additives known per se d).

Component a) is an NCO prepolymer based on the Aus gear components a1) and a2). Component a) has an NCO content of 2 to 20, preferably 2.5 to 18 wt .-% and a content of monomeric Diisocyanate a1) of preferably less than 0.5% by weight. The manufacture of the Component a) is carried out by the known reaction of diisocyanates a1) with insufficient amounts of polyhydroxyl compounds a2) under subsequent removal of excess starting diisocyanate by distillation a1) up to the stated residual content of monomeric diisocyanate. The implementation generally takes place in the temperature range from 20 to 100, preferably 70 to  90 ° C while maintaining an NCO / OH equivalent ratio of 1.5: 1 to 20: 1, preferably 1.8: 1 to 15: 1.

Component a1) is any organic diisocyanate (Cyclo) aliphatically bound isocyanate groups in the molecular weight range 168 to 300. Here, above and below, "(cyclo) aliphatic" means aliphatic and / or cycloaliphatic ".

Examples of suitable diisocyanates a1) are hexamethylene diisocyanate (HDI), 1-iso cyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (IPDI), 4,4'-diisocyanato dicyclohexylmethane (HMDI), its technical mixtures with 2,4'-diisocyanato dicyclohexylmethane or any mixture of such diisocyanates.

Component a2) is any at least two and preferably two alcoholic hydroxyl-containing polysiloxanes Molecular weight range 300 to 5000, preferably 400 to 2500. Die particularly suitable polysiloxanes a2) containing hydroxyl groups correspond to the general formula (I)

in which
R represents an alkyl radical with 1 to 6 carbon atoms, preferably a methyl group,
n is an integer from 1 to 6, preferably 1 and
x represents an integer from 4 to 50, preferably 5 to 20.

Component b) is a known coating polyisocyanate with (cyclo) aliphatic isocyanate groups and a content of  monomeric, distillable diisocyanate of less than 0.5% by weight. The NCO content this polyisocyanate is generally 10 to 25, preferably 13 to 25% by weight. Allophanate, biuret, isocyanurate, oxadiazine, Lacquer polyisocyanates containing uretdione and / or urethane groups, as in known manner by appropriate modification of simple Diisocyanates of the type already exemplified above, in particular by suitable modification of HDI, IPDI or mixtures of HDI and IPDI are accessible. Component b) particularly preferably consists of a Oligomerization of HDI obtained uretdione and isocyanurate groups containing polyisocyanate mixture with an NCO content of 20 to 25 wt .-%, a viscosity (25 ° C) of 100 to 400 mPa · s and a content of monomeric HDI of less than 0.5% by weight.

Any solvent which is inert towards isocyanate groups can be used as solvent c) Solvents of the type known per se into consideration. May be mentioned as an example Toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethylene glycol monoethyl ether acetate, cyclohexane, n-hexane or any Mixtures of such solvents. At least that is particularly advantageous partial use of water-miscible solvents such as for example acetone.

According to a special variant, component c) can at least partially also consist of ortho-silicic acid alkyl esters. Suitable orthosilica esters are, for example, silica tetramethyl ester or silica tetraethyl ester. These special solvents have the dual function of a solvent and a reactive thinner. The silicic acid esters react themselves understandable when exposed to air humidity or when exposed to moisture present in the substrate to be impregnated to form polymeric silica, so that when these special solvents are used the hardening mechanism on this reaction and at the same time on the between NCO groups and water (moisture) occurring crosslinking reaction is based.

In those that may be present in the impregnating agents according to the invention Auxiliaries and additives d) are, for example, cyclic Acid anhydrides such as maleic anhydride, phthalic anhydride or tetrahydro  phthalic anhydride, which are often incorporated into the impregnating agents, if these contain silicic acid esters of the latter type. That acid anhydrides cause the reaction of the silicic acid esters to accelerate Formation of polymeric silica.

Further auxiliaries and additives d) which may be used are included in for example, catalysts that accelerate the isocyanate-water reaction. These catalysts are added to the impregnating agents, if at all, in quantities of up to 8, preferably up to 5 wt .-% added.

Further auxiliaries and additives d) which may be used are for example stabilizers such as benzoyl chloride, surface-active substances or flow aids of the type known per se from paint technology. Also Pigments and fillers can also be used, but this is less prefers.

The use of the impregnating agent according to the invention for impregnating mineral substrates, especially of concrete or natural stone, can according to the usual procedures. The techniques of Splashing, rolling, diving or painting.

Also for draining wet or damp masonry by injection the impregnating agents according to the invention can be used.

In the following examples, unless otherwise stated, all percentages to percentages by weight and all information in "parts" Parts by weight.

Examples 1. Production of NCO prepolymers

• 1.1 Prepolymer from IPDI and an α, ω-hydroxyalkyl-terminated polysiloxane with 6% OH (comparison, according to Example 1.1 of EP-A-0 259 644).
• 1102.5 parts of IPDI (37.8% NCO) are added within one Hour 1400 parts of an α, ω-hydroxymethyl-polydimethylsiloxane des Molecular weight 560 according to the above general Formula (I) added dropwise at 70 to 80 ° C. After the reaction has ended 2.63 parts of benzoyl chloride are added. The isocyanate content is about 8%. The NCO semi-prepolymer contains 7.3% of free IPDI.
• 1.2 prepolymer of IPDI and an α, ω-hydroxyalkyl-terminated polysiloxane with 3% OH.
• The 1154 parts of IPDI (37.84% NCO) are submitted within one Hour 1500 parts of an α, ω-hydroxymethyl-polydimethylsiloxane des Molecular weight 1155 according to the above general Formula (I) added at 70-80 ° C. After the reaction is over 2.8 parts of benzoyl chloride were added.
• The isocyanate content is approximately 12.2%.
• Then the product on the thin film evaporator in the nitrogen Ge counter current at 190 ° C evaporation surface temperature and 0.6-0.8 mbar exempt from unconverted IPDI down to a residual content of 0.1%. The practically monomer-free NCO prepolymer thus obtained has one NCO content of 4.9%.
• 1.3 Prepolymer from IPDI and an α, ω-hydroxyalkyl-terminated poly siloxane with 6% OH.  
• 1567 parts of IPDI (37.84% NCO) are submitted within one Hour 1000 g of an α, ω-hydroxymethyl-polydimethylsiloxane of the mole molecular weight 560 according to the above general Formula (I) added at 70-80 ° C. After the reaction is over 2.7 parts of benzoyl chloride were added. The isocyanate content is 16.7%. Then the reaction product as in 1.2 described by monomeric IPDI down to a residual content of 0.54% exempted. The NCO prepolymer thus obtained has an NCO content of 6.8%.
• 1.4 prepolymer from a mixture of IPDI and tris (isocyanatohexyl) biuret and the above-mentioned polysiloxane with 6% OH (comparison corresponding to Example 1.3 of EP-A-0259 644).
• 111 parts IPDI and 190.9 parts tris (isocyantohexyl) biuret (23% NCO) are introduced with stirring and at a temperature of 70 to 80 ° C. 300 parts of the above polysiloxane was added dropwise. After completing the 0.5 parts of benzoyl chloride are added to the reaction. The isocyanate content the conversion product is 6.1%; the content of free IPDI 4.4%; the viscosity (25 ° C) at 718,000 mPa · s.

2. Manufacture of impregnation agents

• In the examples according to the invention below, the component b) always a technical lacquer polyisocyanate with an NCO content of 22.5, a content of monomeric HDI of 0.1% and a viscosity (25 ° C) of 200 mPa · s. It is this lacquer poly isocyanate around a uretdione group and isocyanurate groups Modification product from HDI. The weight ratio of uretdione diisocyanates to polyisocyanates containing isocyanurate groups at approx. 2: 1.  
• 2.1 (comparison)
  25 parts of the NCO semiprepolymer according to 1.1 are dissolved in 75 parts of n-butyl acetate to form a ready-to-use impregnating agent.
• 2.2 (according to the invention)
  23 parts of the prepolymer according to 1.2 are dissolved together with 2 parts of the above-mentioned lacquer polyisocyanate b) in 75 parts of n-butyl acetate to form a ready-to-use impregnating agent.
• 2.3 (according to the invention)
  22 parts of the NCO prepolymer according to 1.2 are dissolved together with 3 parts of the above-mentioned lacquer polyisocyanate b) in 75 parts of n-butyl acetate to form a ready-to-use impregnating agent.
• 2.4 23 parts of the NCO prepolymer according to 1.3 are together with 2 parts of the above-mentioned lacquer polyisocyanate b) in 75 parts n-Butyl acetate dissolved in a ready-to-use impregnating agent.
• 2.5 22 parts of the NCO prepolymer according to 1.3 are together with 3 parts of the above-mentioned lacquer polyisocyanate b) in 75 parts n-Butyl acetate dissolved in a ready-to-use impregnating agent.

3. Impregnation tests on Ebenheider sandstone

• Stone prisms made of Ebensheid sandstone (dimensions 5 × 5 × 10 cm), which are coated on the outer surface with a dense epoxy resin, are placed with one unsealed side at normal atmospheric pressure in one of the impregnating agents mentioned and left there for 4 hours. By smashing the prisms in the longitudinal direction, the penetration depth a) directly after the impregnation,
  b) tested after 28 days of curing.

4. Measurement of the brittleness of the stone depending on the depth of penetration (Distance from surface)

• The prisms described above are cut into thin slices (4 mm) and their modulus of elasticity is determined. For this purpose, the 4 mm thick, parallel cut discs are stored in a specially designed apparatus on a support ring with an inner diameter of 40 mm and applied with a concentric loading ring with an outer diameter of 26.7 mm with a force F. During this process, the deflection of the stone that bulges under the action of force from the rest position is measured as a function of the force. If you apply the tension (force related to the circular area of the load ram) against the elongation (deflection from the rest position), the elastic modulus can be determined by graphical evaluation as the slope of the stress-strain line. Below are some of the elasticity modules determined in this way at different penetration depths:

Claims (3)

1. Impregnating agent consisting essentially of

• a) 100 parts by weight of an NCO prepolymer with an NCO content of 2 to 20% by weight and a content of monomeric diisocyanate
  • a1) from less than 1% by weight
  • a1) (Cyclo) aliphatic diisocyanates of the molecular weight range 168 to 300 and
  • a2) at least two alcoholically bound hydroxyl-containing polysiloxanes of the molecular weight range 300 to 5000,
• b) 5 to 150 parts by weight of at least one silicon-free, allophanate, biuret, isocyanurate, oxadiazine, uretdione and / or urethane groups containing paint polyisocyanate with a content of (cyclo) aliphatically bound isocyanate groups of 10 to 25 % By weight and a monomeric diisocyanate content of less than 0.5% by weight,
• c) 100 to 1000 parts by weight of a solvent component, consisting of at least one solvent which is inert to isocyanate groups,
  and if necessary
• d) other auxiliaries and additives.

2. Impregnating agent according to claim 1, characterized in that component a2) is a polysiloxane of the formula (I) acts where
R represents a methyl group, and
x represents a number from 4 to 50. 3. Use of the impregnating agent according to claim 1 and 2 for Impregnation of mineral substrates, especially concrete or Natural stone.