DE19706904A1 - Non-waterproofing impregnating material for concrete and stone etc. - Google Patents

Abstract

Impregnating material (A), derived from (a) 100 pts. wt.NCO-prepolymer with an NCO content of 2-20 wt% and a monomeric di-isocyanate content (a1) of less than 1 wt% based on (a1) (cyclo)aliphatic di-isocyanates with mol. wts. of 168-300 and (a2) polyethers, polyesters, polylactones or polyamides of mol. wt. 300-5000 with at least two alcoholic hydroxyl groups, (b) 5-150 pts. wt. silicon-free paint polyisocyanate(s) with allophanate, biuret, isocyanurate, oxadiazine, uretedione and/or urethane groups, containing 10-25 wt% (cyclo)aliphatic isocyanate groups and with a monomeric di-isocyanate content of less than 0.5 wt%, (c) 100-1000 pts. wt. solvent component containing at least one solvent which is inert towards NCO groups, and optionally (d) other additives etc.

Description

The invention relates to a new impregnating agent for mineral substrates based a special mixture of compounds containing isocyanate groups and its use for the impregnation of mineral substrates.

The use of organic polyisocyanates as essential components of Impregnation agents for mineral substrates are known. For example, describes EP-A-0 287026 a method for protecting, restoring or restoring stone structures by treatment with a solution of aliphatic isocyanates. EP-A-0 259 644 describes impregnating agents for mineral substrates based on of NCO prepolymers or semiprepolymers from (cyclo) aliphatic diisocyanates naten and alcoholic hydroxyl-containing polysiloxanes. So were at the preparation of the prepolymers for removal of unreacted excess diisocyanate is dispensed with.

DE-A 19 503 284 describes an impregnating agent for mineral substrates, the essentially from a mixture of those described in EP-A-0259644, however prepolymers freed from unconverted isocyanate with allophanate, biuret, isocya lacquer polyiso containing nurate, oxadiazine, uretdione and / or urethane groups cyanates exist. These blends have improved penetration in mineral substrates.

All these impregnating agents have in common that they me the mineral substrate consolidate mechanically and cause the mineral substrate to become hydrophobic.

Many tasks in the field of building protection and stone preservation tion require an improvement in the mechanical properties of the stone without to make it hydrophobic at the same time. This is the case with the masonry sanie, for example tion, especially with brick masonry, hydrophobing is rather undesirable because this strongly resuspended the renovated masonry with fresh mortar disabled, often even impossible. In such a case, the  Hydrophobicity of the substrate does not properly couple the fresh grout ales with the renovated building fabric.

Another problem is the salinity of buildings, which is caused by rising Moisture arises as a transport medium for salts from the underground. Salt pollution are often disruptive for impregnation and impregnation attempts of any kind.

It was therefore the object of the invention to provide an impregnating agent To provide that has a stone-strengthening effect, but not the stone makes hydrophobic. In addition, with regard to depth of penetration and impregnation hold with the impregnating agent of the prior art at least equivalent To deliver products that also meet industrial hygiene and ecological requirements fully correspond to (products free of isocyanate).

Furthermore, the impregnating agent should also be applicable to salty stone, and there also an unrestricted stone-strengthening but not hydrophobicizing we unfold.

This task was accomplished with the provision of the impregnating agents according to the invention be solved.

The invention relates to impregnating agents

• 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 have the polyethers, polyesters, polylactones or polyamides 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 Lacquer polyisocyanate containing (cyclo) aliphatically bound iso cyanate groups of 10 to 25 wt .-% and a content of monomeric Diisocyanate 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.

The invention also relates to the use of these impregnating agents for im 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 contain given if necessary, 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 production of component a) is carried out by known reaction of diisocyanates a1) with deficit Amounts of polyhydroxy compounds a2) followed by removal by distillation tion of excess starting diisocyanate a1) up to the stated residual content of monomeric diisocyanate. The reaction is generally carried out in 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: 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-isocya nato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (IPDI), 4,4'-diisocyanatodicyc lohexylmethane (HMDI), whose technical mixtures with 2,4'-diisocyanatodicyclo hexylmethane or any mixture of such diisocyanates.

Component a2) is any at least two alcoholic ones Polyethers, polyesters, polylactones and polyamides of hydroxyl groups Molecular weight range 300 to 5000, preferably 400 to 2500, as for the Production of both cellular and non-cellular polyurethanes are known per se.

Mixtures of various such compounds are also suitable according to the invention Question.

Polyethers of the following structure are preferably used as component a2):

in which
R ₁ , R _{2 represents} H or CH ₃ with the proviso that one of the radicals R ₁ or R ₂ must always be hydrogen,
M is a straight-chain or branched hydrocarbon radical with 2 to 12 carbon atoms, which may optionally contain heteroatoms such as N, S, O.
X for a number from 3 to 110 and
n stands for a number from 2 to 4.

Component b) is a known coating polyisocyanate with (Cyclo) aliphatically bound isocyanate groups and a content of monomeric, distillable diisocyanate of less than 0.5% by weight. The NCO content of this polyiso cyanate is generally 10 to 25, preferably 13 to 25 wt .-%. Suitable are allophanate, biuret, isocyanurate, oxadiazine, uretdione and / or urethane groups pen-containing lacquer polyisocyanates, as ent in a manner known per se Descriptive modification of simple diisocyanates already exemplary above mentioned type, in particular by suitable modification of HDI, IPDI or Mixtures of HDI and IPDI are accessible. This is particularly preferred Component b) from a uretdione and obtained by oligomerization of HDI Polyisocyanate mixture containing isocyanurate groups and having an NCO content of 20 to 25 wt .-%, a viscosity (25 ° C) of 100 to 400 mPas 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) means of the type known per se. Called his toluene as an example, Xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, Ethylene glycol monomethyl ether acetate, cyclohexane, n-hexane or any mixture such solvents. The at least partially Mit is particularly advantageous use of water-miscible solvents such as acetone.

According to a special variant, component c) can at least partially consist of ortho-silicic acid alkyl esters. Suitable orthosilica esters are available at for example, silica tetramethyl ester or silica tetraethyl ester. This spe Ziell solvents have the dual function of a solvent and one reactive thinner. Of course, the silicic acid esters react with the Exposure to atmospheric moisture or to the impact the substrate present moisture to form polymeric pebbles acid so that when these special solvents are used, the hardening mecha  on this reaction and at the same time on that 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 tetrahydrophthalic anhydride, which are often incorporated into the impregnating agents when they contain silica contain esters of the latter type. These acid anhydrides cause a loading acceleration of the reaction of the silica esters with the formation of polymeric silica acid.

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

Further auxiliaries and additives d) which may be used are examples wise stabilizers such as benzoyl chloride, surface-active substances or flow tools of the kind known per se from paint technology. Also pigments and Fillers can be used, but this is less preferred.

The use of the impregnating agent according to the invention for impregnating mi mineral substances, especially of concrete or natural stone but also of Masonry, especially brick masonry, can be done using the usual methods respectively. The techniques of splashing, rolling, dewing are mentioned here as examples chens or deletions.

Examples

Unless stated otherwise, all percentages in the examples relate to one another to percentages by weight and all information in "parts" to parts by weight.

1. Preparation of an isocyanate prepolymer as an impregnating agent

168 g of hexamethylene diisocyanate (nNCO = 2.0 mol) are placed at 60 ° C and 100 g of a pure propylene oxide chain started on glycerin Polyether with an OH number of 250 mg KOH / g (nOH 0.446 mol) still admit. The reaction mixture is stirred until the Isocyanate content reached 24%. Then the semi-prepolymer is desti lation on the thin film evaporator from the excess hexamethylene diiso cyanate freed (distillation conditions: 160 ° C jacket temperature at 0.4 mbar); the prepolymer is obtained as a viscous liquid (140 g, NCO = 10.3%, Viscosity at 25 ° C = 10951)

2. Production of the impregnating agent

For the experiments in the examples below, component b) is used Technical lacquer polyisocyanate with an NCO content of 22.5, one Monomeric HDI content of 0.1% and a viscosity (25 ° C) of 200 mPas used. This lacquer polyisocyanate is a uret Modification product having dione groups and isocyanurate groups from HDI. the weight ratio of uretdione diisocyanates to isocyanurate group-containing polyisocyanates is approximately 2: 1.

23 parts of the NCO prepolymer according to 1. together with 2 parts the above-mentioned lacquer polyisocyanate b) in 75 parts of n-butyl acetate Ready-to-use impregnating agent dissolved.  

3. Impregnation tests on natural stone samples

Stone prisms made of natural stone (dimensions 5 × 5 10 cm), which on the outer surfaces are coated with a dense epoxy resin, each with a unsealed side at normal atmospheric pressure in one of the named Impregnating agent introduced and left there for 4 hours.

3.1 Measuring the depth of penetration

To determine the penetration depth, the stone prism is at least after Sawed into 4 mm thick slices for 28 days and then samples of these disks by elemental analysis for their carbon content checked. The carbon values determined are an indicator variable for the amount of polymeric organic introduced by impregnation Substance. The following table provides an overview of the found Values. The value at 88 mm depth is for comparison, since here a unimpregnated stone is present.

Table 1

The values show that at Ebenheider sandstone at 50 mm and at Sander reed sandstone at approx. 40 mm the level of the untreated Steins in carbon content is reached.

3.2. Determination of the strength and the modulus of elasticity depending on the Depth of penetration (distance from surface)

The prisms described above become 45 mm cores Drilled out diameter.

The drill cores are cut into thin slices (4 mm) and whose modulus of elasticity is determined. The 4 mm thick, plane-parallel cut discs in a specially designed disc Apparatus on a support ring with an inner diameter of 40 mm stored and by means of a concentric load ring with an outer diameter of 26.7 mm with a force F acted upon. During this process, a sensor is used the deflection of the stone bulging under the force measured from the rest position depending on the force. You wear it the tension (force related to the circular area of the load stamp) against the stretch (deflection from the rest position), see above can graphically evaluate the modulus of elasticity as a slope the stress-strain line can be determined. Be below some elastic modulus determined in this way for various Penetration depths communicated:

• a) at Sander Schilfsandstein
  

  Table 2

• b) at Ebenheider sandstone
  

  Table 3

The values show that in the Ebenheid sandstone the strengthening we Polymer impregnation is not yet full at approx. 40 mm impregnation depth has dropped to the level of the impregnated stone.

However, this is the case with Sander Schilfsandstein.

3.3 Experiments with saline natural stones

For the experiments with salty natural stones, as in Ab Section 3.2 described, from drill cores with a diameter of 45 mm stone slabs obtained from Cotta sandstone with a thickness of 4 mm complete soaking with a saline solution. This Solution contained 10.4 g magnesium nitrate hexahydrate, 5.1 g anhydrous Potassium nitrate, 2.6 g anhydrous sodium nitrate and 1.8 g anhydrous Sodium chloride in one liter of deionized water. The stone shit ben were then dried and, as in section 3.1. described, impregnated with the impregnating agent. The curing time was 28 days. For comparison purposes have not been added impregnated stone discs tested and also those that a wet-dry alternating climate and water absorption had undergone testing. There were 5 stone slices each as in section 3.2. described for bending tensile strength and the values are summarized in the table below.  

Overview of the test specimens

Table 4

Table 4 shows that the moisture treatment for the stone slices E and F have only minor losses with modulus of elasticity and flexural strength to D (also saline and impregnated). As a general rule the loss of strength through exposure to salt appears in comparison C (without) to D (salt-treated) also relatively low.

For Cotta sandstone and the salt mixture described above thus the improvement effect of the impregnating agent in relation to the intended consolidation is almost unlimited.

Claims (3)

1. Impregnation agent

• 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 of the molecular weight range 168 to 300 and
  • a2) at least two alcoholically bound hydroxyl groups on pointing polyethers, polyesters, polylactones or polyamides 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 lacquer 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 toward isocyanate groups,
  and if necessary
• d) other auxiliaries and additives.

2. Impregnating agent according to claim 1, characterized in that component a 2) is a polyether of the formula (I)
in which
R ₁ , R _{2 represents} H or CH ₃ with the proviso that one of the radicals R ₁ or R ₂ must always be hydrogen,
M is a straight-chain or branched hydrocarbon radical with 2 to 12 carbon atoms, which may optionally contain heteroatoms such as N, S, O.
X for a number from 3 to 110 and
n stands for a number from 2 to 4. 3. Use of the impregnating agent according to claim 1 for impregnating mineral substrates, in particular of concrete or natural stone and / or Masonry.