New phthalate-free isocyanurate composition and use thereof

Abstract

The present invention relates to new low-monomer, low-viscosity, low-volatility compositions that are highly effective and consist of isocyanate group-containing isocyanurates and a phthalate-free plasticizer, and which, when used as adhesion promoters, result in improved adhesion, to coating agents on the basis of plasticized PVC and to coated substrates.

Description

[0001] New phthalate-free isocyanurate compositions and their use

[0002] The present invention relates to the technical field of adhesion promoters, in particular adhesion promoters for coating agents based on plasticized PVC, and provides phthalate-free, low-monomer, low-viscosity and low-volatility compositions which are eminently suitable as adhesion promoters.

[0003] State of the art

[0004] It is known that the adhesion of plasticized PVC to substrates can be improved by adding an isocyanate-containing adhesion promoter to the plasticized PVC. Such improved adhesion is important, for example, when producing synthetic textiles with a PVC coating. Isocyanurates containing isocyanate groups are preferred as adhesion promoters. These can be produced from diisocyanates by oligomerization, including trimerization. Commercially available mixtures of the isomeric diisocyanatotoluenes (TDI), consisting primarily of 2,4-diisocyanatotoluene (2,4-TDI) and 2,6-diisocyanatotoluene (2,6-TDI), are normally used as diisocyanates. These can be easily converted almost completely into isocyanate-containing isocyanurates.Almost complete conversion is required for reasons of occupational and product safety, as well as EU regulations, which is why the residual content of monomeric diisocyanates in the adhesion promoter composition is kept below 0.5 wt.%. Diisocyanatodiphenylmethanes (MDI), which are also readily available, are less suitable. They are more difficult to trimerize than TDI and can thus lead to an undesirably high residual diisocyanate content. Furthermore, MDI-based isocyanurates containing isocyanate groups exhibit poor solubility and are prone to crystallization.

[0005] Isocyanurates containing isocyanate groups

[0006] Isocyanurates containing isocyanate groups are particularly easy to handle as adhesion promoters when used as a solution in a plasticizer. The preparation of the isocyanate-containing isocyanurates from TDI preferably takes place in the plasticizer used as a solvent. Such adhesion promoters and plasticizer-containing adhesion promoter compositions, their preparation, and their application are described, for example, in DE2419016 A1 (GB1455701 A), WO 2011 / 095569, or WO 2021 / 239621 A1. Plasticizer and plasticized PVC

[0007] Plasticizers within the meaning of the present invention are typically non-volatile or only slightly volatile organic substances that do not form a covalent bond with PVC and lower its glass transition temperature. By mixing with the plasticizer, the inherently hard and brittle PVC is converted into a soft, tough material known to those skilled in the art as plasticized PVC or soft PVC. The plasticized PVC is usually a flexible solid at room temperature. Suitable plasticizers are known to those skilled in the art. Typical plasticizers are, for example, esters of phthalic acid, terephthalic acid, sebacic acid, trimellitic acid, alkanesulfonic acid, citric acid or benzoic acid with monoalcohols. Plasticized PVC contains significant amounts of such plasticizers, which usually range from 10 wt.% to over 50 wt.% of the total mass of the plasticized PVC.Under unfavorable usage conditions, the plasticizer can migrate to the surface or migrate into neighboring materials. Therefore, the use of plasticized PVC poses a risk of contamination of humans and the environment with the plasticizer. In light of this problem, there has recently been an increasing demand that the plasticizers used be harmless to humans and non-bioaccumulative.

[0008] Short-chain phthalates as plasticizers

[0009] According to the REACH directive applicable in the European Union, the plasticizers di(2-ethylhexyl) phthalate, dibutyl phthalate, and benzyl butyl phthalate are on the SVHC (substances of very high concern) list. Furthermore, the plasticizers diisononyl phthalate, diisodecyl phthalate, and di-n-octyl phthalate are no longer permitted for use in toys or baby products that children can put in their mouths. Given these restrictions, which may seem confusing and unsettling to some consumers, many manufacturers are generally omitting all phthalate-containing plasticizers and their isomers from the production of plasticized PVC. Therefore, there is a need for phthalate-free plasticizers that achieve the performance levels of phthalate-based plasticizers in terms of processability and performance properties. Phthalate-free plasticizers

[0010] In the context of the present invention, phthalate-free plasticizers are plasticizers which - based on the plasticizer content - contain less than 1.0 wt.%, preferably less than 0.5 wt.%, particularly preferably less than 0.1 wt.% and particularly preferably no phthalic acid dialkyl esters.

[0011] Phthalate-free adhesion promoter compositions

[0012] The elimination of phthalate-containing plasticizers is now also required for plasticizer-containing adhesion promoter compositions, particularly for sensitive applications involving, for example, skin contact. There is therefore a great need for adhesion promoter compositions that do not contain phthalates but still exhibit the good adhesion properties of phthalate-containing adhesion promoter compositions from the prior art. In the context of the present invention, phthalate-free adhesion promoter compositions are those which—based on their total mass—contain less than 1.0 wt. %, preferably less than 0.5 wt. %, particularly preferably less than 0.1 wt. %, and particularly preferably no dialkyl phthalates.

[0013] Furthermore, the adhesion promoter compositions are required to be clear, as colorless as possible, and free of solids or precipitates. They must not contain highly volatile components, i.e., organic compounds with a boiling point below 100°C. For good processability, they must have a viscosity at 23°C of less than 30,000 mPa s, preferably less than 15,000 mPa s, and particularly preferably less than 10,000 mPa s. The residual content of monomeric diisocyanates should be less than 0.5% by weight.

[0014] For example, the adhesion promoter compositions based on diisononyl phthalate described in WO 2005 70984 A1 are less suitable for sensitive applications. DE 2551634 A1 and EP 1378529 A1 postulate that suitable adhesion promoters, TDI-based isocyanurates containing isocyanate groups, can be prepared in any solvent, including phthalate-free plasticizers. However, this is not the case. Experiments by the inventors have shown that not just any phthalate-free plasticizers lead to adhesion promoter compositions that meet all of the described requirements. This also applies to the plasticizers based on alkanesulfonic acid esters of phenol (ASE), which are marketed under the trade name Mesamoll®, described in DE 102007034977. DE 3041732 A1 describes solutions of isocyanurates containing isocyanate groups that are suitable as adhesion promoters, although these are prepared from MDI.These solutions are unsuitable for the reasons mentioned above.

[0015] Object of the invention

[0016] The object of the present invention was therefore to provide compositions of isocyanurates containing isocyanate groups that are suitable as adhesion promoters. Although they contain phthalate-free plasticizers, their mechanical properties, such as adhesive strengths, achieve the level of the phthalate-containing adhesion promoter compositions from WO2005 / 70984 A1. The isocyanurates containing isocyanate groups should ideally be based on industrially available isomer mixtures of TDI. The compositions should be clear and virtually colorless, their viscosity at 23 °C should be less than 30,000 mPa s, preferably less than 20,000 mPa s, and particularly preferably less than 10,000 mPa s, and the content of free TDI (all isomers) should ideally be less than 0.50 wt. %. The volatility of the plasticizer used should not be higher than that of the isononyl benzoate.

[0017] Volatility of the plasticizer

[0018] The volatility of the plasticizer used should not be less favorable than that of isononyl benzoate (INB). INB is accepted worldwide as a carrier for the isocyanate-containing isocyanurate-based adhesion promoter, but is no longer available. However, higher volatility is undesirable. The volatility of a substance is determined using thermogravimetric analysis (TGA).

[0019] Solution to the task

[0020] Compositions comprising: a) isocyanurates containing isocyanate groups and b) alkylenediol dibenzoate, wherein the weight ratio of a) to b) is in the range from 1:1 to 1:8, preferably from 1:1.2 to 1:4, and particularly preferably from 1:1.5 to 1:2.5. In a preferred embodiment, the alkylenediol benzoate contains, as the alkylene group, a branched or unbranched C2 to C8 alkylene group, preferably a branched or unbranched C2 to C10 alkylene group.

[0021] The use of 1,2-propanediol dibenzoate as component b) is particularly preferred.

[0022] In a preferred embodiment of the invention, the compositions contain 20 to 35 wt.% of isocyanurates containing isocyanate groups and 80 to 65 wt.% of 1,2-propanediol dibenzoate

[0023] In a preferred embodiment, the compositions contain up to 50 wt.%, preferably 0.1 to 40 wt.%, of one or more diluents, based on the total mass of the composition. These diluents are preferably selected from the group consisting of alkyl acetate, preferably butyl acetate, ethyl acetate, propyl acetate, N-alkylpyrrolidone, N-octylpyrrolidone, N-decylpyrrolidone, DMF, acetone, alkyl benzoates, preferably benzyl benzoate, paraffins, white oils, and low-aromatic aliphatics, as well as mixtures of these substances.

[0024] In a further preferred embodiment, the composition does not contain any diluents.

[0025] Isocyanurates containing isocyanate groups can advantageously be used as component a), which are obtainable by oligomerization of a mixture of isomeric diisocyanatotoluenes containing 2,4-diisocyanatotoluene and 2,6-diisocyanatotoluene.

[0026] Isocyanurates containing isocyanate groups are preferably used as component a), which are obtainable by oligomerization of a mixture of 65 to 95% by weight of 2,4-diisocyanatotoluene and 5 to 35% by weight of 2,6-diisocyanatotoluene, the percentages by weight being based in each case on the total amount of diisocyanatotoluenes.

[0027] The preparation of component a) can be carried out by oligomerization of the diisocyanate mixtures according to known processes, as described, for example, in WO 2005 70984 A1.

[0028] The oligomerization is preferably carried out in the presence of the plasticizer component b).

[0029] In a preferred embodiment, the total proportion of components a) and b) in the compositions is at least 50% by weight, preferably at least 75% by weight, particularly preferably at least 85% by weight, very particularly preferably at least 92% by weight, and most preferably between 95 and 100% by weight.

[0030] The present invention also relates to a process for preparing the compositions according to the invention, in which diisocyanates are oligomerized in the presence of the dibenzoate b) to the isocyanate group-containing isocyanurates a).

[0031] The oligomerization typically occurs in the temperature range of 40 to 140 °C, preferably 40 to 80 °C. The oligomerization is typically terminated when the content of monomeric diisocyanates in the reaction mixture is 0.49 wt.% or less.

[0032] Such termination can be achieved by complete or partial deactivation of the catalyst, for example by thermal decomposition of the catalyst or addition of a reaction stopper. Protic acids, acid chlorides, or methylating compounds can be used as reaction stoppers. Alkyl phosphates, in particular dibutyl phosphate or methyl toluenesulfonate, are particularly preferred. Typically, when a reaction stopper is used, it is used in an amount of 0.02 to 4% by weight, preferably 0.02 to 2% by weight, particularly preferably 0.02 to 1% by weight, based on the total amount of diisocyanate used. The product then typically contains 3 to 7% by weight, preferably 4.5 to 6.5%, of isocyanate groups.

[0033] In a preferred embodiment, the diisocyanates used in the process according to the invention are diisocyanatotoluenes, particularly preferably industrially available mixtures consisting essentially of 2,4-TDI and 2,6-TDI. The mixtures are mixtures of isomeric diisocyanatotoluenes containing 65 to 95 wt. % 2,4-diisocyanatotoluene and 5 to 35 wt. % 2,6-diisocyanatotoluene and are prepared under catalysis. The TDI isomer mixtures particularly preferably contain 75 to 85 wt. % 2,4-TDI mixed with 15 to 25 wt. % 2,6-TDI. An example of these particularly preferred TDI isomer mixtures is the product Desmodur® T80, commercially available from Covestro AG.

[0034] To prepare component a), a catalyst can be used to initiate and accelerate the oligomerization, which leads to the selective incorporation of TDI even at elevated temperatures. Such catalysts contain N,N-dialkylaminomethyl groups and phenolic OH groups (alkyl: C1-C3 alkyl chain and / or alkylene chain with 1 to 18 carbon atoms, optionally separated by oxygen or sulfur) bound to aromatics. These groups can be distributed over several molecules or positioned on one or more aromatic rings. Compounds containing both hydroxyl and aminomethyl groups in one molecule are preferably used as catalyst systems.

[0035] Particularly preferred systems are those in which C1-C3 dialkylaminomethyl groups are positioned ortho to aromatic hydroxyl groups.

[0036] The synthesis of Mannich bases suitable as catalysts is described, for example, in DE 25 51 634 A1 and WO 2005 70984 A1. Mannich bases to be used preferably are those based on phenol, p-isononylphenol, or bisphenol A, which are obtained by reaction with dimethylamine and formaldehyde, for example, according to DE-A 2 452 531 or Synth. Commun. (1986), 16, 1401-9. Mannich bases based on phenol or bisphenol A are particularly preferred.

[0037] The catalysts to be used are used as pure substances or dissolved, preferably in several small portions or continuously.

[0038] The compositions according to the invention are clear, colorless or almost colorless liquids with surprising storage stability, exhibiting no tendency toward discoloration, crystallization, precipitation, or phase separation even after several weeks of storage. Furthermore, they are characterized by an extremely low content of free TDI (i.e., monomeric diisocyanatotoluenes) before and after storage, which is a particular advantage of the compositions according to the invention due to the relatively low boiling point of this toxicologically hazardous diisocyanate.

[0039] The comparative examples 1 to 6 listed below thus not only show that the object underlying this invention cannot be achieved with any phthalate-free plasticizers, but also demonstrate that the present invention also provides a process with which the combination of plasticizer and isocyanate-containing isocyanurates can be advantageously produced, which provides the required properties as adhesion promoter compositions.

[0040] Use of the compositions according to the invention

[0041] The compositions according to the invention are suitable as adhesion promoters, particularly for coatings made of plasticized PVC, or as adhesion-promoting additives for PVC plastisols. Those skilled in the art understand PVC plastisols to be liquid dispersions of PVC in a plasticizer, which gel, for example, upon heating to a higher temperature and can thus be used to produce plasticized PVC. The compositions according to the invention can be used particularly advantageously as adhesion promoters between substrates made of synthetic fibers with groups reactive toward isocyanate groups, such as polyamide or polyester fibers, and PVC plastisols or soft PVC melts. Of course, the solutions according to the invention can also be used to improve the adhesion of plasticized PVC to flat substrates, such as films.

[0042] The compositions according to the invention are therefore particularly suitable as adhesion promoters for coating compositions based on plasticized PVC. For the purposes of the present invention, the term "coating composition based on plasticized PVC" encompasses both coating compositions containing plastisols and coating compositions that are applied to the substrate in the form of compositions containing molten plasticized PVC, with the former being preferred.

[0043] Textiles and fabrics, especially those made of natural, synthetic, or glass fibers, are particularly suitable as substrates for coating. Polyamide and polyester fibers are particularly suitable as synthetic fibers. Leather can also be used as a substrate.

[0044] The compositions according to the invention can be used to produce substrates with coatings containing or consisting of plasticized PVC. If the coating does not consist of plasticized PVC, it typically contains at least 50% by weight, preferably at least 75% by weight, and particularly preferably from 90% by weight to 99% by weight of the same, in addition to the additives for PVC coatings customary to those skilled in the art. For example, the compositions according to the invention can be printed, knife-coated, screen-coated, sprayed, or applied by dipping onto the substrates to be coated. Depending on the article to be produced, one or more adhesion promoter-free PVC layers are applied to the thus pretreated substrate surfaces, e.g., as plastisols, by extrusion or melt roll coating, or by lamination.Particularly preferably, the compositions according to the invention can also be added to a PVC plastisol before its application.

[0045] The compositions according to the invention are typically used in amounts such that, based on the plasticizer-free PVC of the coating composition, 0.5 to 40 wt.%, preferably 2 to 15 wt.%, of isocyanurates containing isocyanate groups are present. However, the solutions according to the invention can also be used in any other amounts adapted to the respective field of application.

[0046] The production of the finished layers, i.e. the reaction of the isocyanate groups of the adhesion promoter with the substrate and the gelling of the PVC layer, is carried out in the usual way at higher temperatures, regardless of the type of application, whereby temperatures between 110 and 210°C are used depending on the composition of the PVC layers.

[0047] The present invention further provides coatings and coated substrates for textiles or fabrics, which are obtainable using the adhesion promoter compositions described above. The compositions according to the invention are suitable as adhesion promoters for coating compositions based on plasticized PVC, and thus for the production of coatings containing or consisting of plasticized PVC, ie, in particular for the production of tarpaulins, billboards, air-supported structures and other textile structures, flexible containers, tent roofs, awnings, protective clothing, conveyor belts, flock carpets, or foam synthetic leather.

[0048] The compositions according to the invention are particularly suitable as adhesion-promoting additives in the coating of substrates with groups reactive towards isocyanate groups, in particular in the coating of yarns, mats and fabrics made of polyester or polyamide fibres.

[0049] Example and comparison examples

[0050] Unless otherwise noted, all parts and percentages are by weight.

[0051] Determination of the key data

[0052] The product characteristics were determined by viscosity at 23°C (rotational viscometer VT550 from Haake GmbH, Karlsruhe) and the free TDI content (gas chromatography, Hewlett Packard 5890 according to DIN ISO 55956). The isocyanate content was determined according to EN ISO 11909. The TGA curves were generated using a Mettler Toledo TGA / DSC 3+ SF / 1100 / 189, T = RT to 400°C, 10°C / min, N2. Starting materials for example and comparative examples

[0053] Desmodur® T80: TDI isomer mixture of 80 wt% 2,4-TDI and 20 wt% 2,6-TDI, Covestro AG.

[0054] Vestinol® 9 DI NP: diisononyl phthalate, Evonik AG.

[0055] Adimoll® DB: Dibutyl adipate, Lanxess Deutschland GmbH.

[0056] Adimoll® DO: Dioctyl adipate, Lanxess Deutschland GmbH.

[0057] Modulast® PUR: 1,2-propanediol dibenzoate, Lanxess Deutschland GmbH.

[0058] Catalyst: DABCO TMR 30 (2,4,6-Tris(dimethylaminoethyl)phenol), Evonik AG.

[0059] Reaction stopper: Dibutyl phosphate, Lanxess Deutschland GmbH.

[0060] TGA:

[0061] Table 1 : Determination of the volatility of various plasticizers in comparison to the plasticizer DINP by TGA

[0062] Table 1 shows that dibutyl adipate (DBA) has largely evaporated at typical processing temperatures for PVC plastisols. This is unacceptable for environmental and occupational safety reasons. Furthermore, it can lead to blistering in the PVC layer, which is also extremely undesirable. (not according to the invention) DINP

[0063] 180 parts by weight of Desmodur® T80 were trimerized at 55 °C in 378 parts by weight of Vestinol® 9 DINP with 1.6 parts by weight of catalyst. After 72 hours, the reaction was interrupted by adding 2.6 parts by weight of reaction stopper and stirred for three hours at 60 to 70 °C. A clear, colorless solution with an isocyanate content of 5.53 wt.%, a viscosity at 23 °C of 41,400 mPas, and a free TDI content of 0.14 wt.% was obtained. (not according to the invention) DBA

[0064] The volatility of dibutyl adipate was previously determined using TGA (see Table 1).

[0065] It was found that the material evaporates almost completely at typical PVC processing temperatures of 180-210 °C. This can lead to blistering in the PVC layer and is therefore extremely undesirable. Further testing was therefore omitted. (not according to the invention) Mesamoll® II 2.9 T Kat

[0066] 180 parts by weight of Desmodur® T80 were trimerized at 55 °C in 504 parts by weight of Mesamoll® II with 2.9 parts by weight of catalyst. After 72 hours, the reaction was interrupted by adding 4.7 parts by weight of reaction stopper and stirred for three hours at 60 to 70 °C. A clear, yellowish solution with an isocyanate content of 4.8 wt.%, a viscosity at 23 °C of 11,600 mPas, and a free TDI content of 0.25 wt.% was obtained. (not according to the invention) Mesamoll® II 1 ,5 T Kat

[0067] 180 parts by weight of Desmodur® T80 were trimerized at 55 °C in 378 parts by weight of Mesamoll® II with 1.5 parts by weight of catalyst. After 72 hours, the reaction was interrupted by adding 2.6 parts by weight of reaction stopper, and the mixture was stirred for three hours at 60 to 70 °C. A clear, yellowish solution with an isocyanate content of 5.31 wt.%, a viscosity at 23 °C of > 300,000 mPas, and a free TDI content of 0.15 wt.% was obtained. (not according to the invention) Dioctyl adipate

[0068] 180 parts by weight of Desmodur® T80 were trimerized at 70°C in 534 parts by weight of Adimoll DO with 2.5 parts by weight of catalyst. After 5 hours, the reaction was interrupted by adding 5 parts by weight of reaction stopper, and the mixture was stirred for 1 hour at 60 to 70°C. No clear solution was obtained. After a short time, a precipitate formed. The product is unusable in this state and was not analyzed further. Comparative Example 1 corresponds to Example 2 of EP 1 711 546 A1 and serves to compare the properties of the adhesion promoter compositions according to the invention with the prior art. Comparative Examples 3 and 4 demonstrate that increasing the amount of catalyst does not automatically lead to a product according to the invention.

[0069] As non-inventive Comparative Examples 1 to 5 further demonstrate, the choice of plasticizer has a decisive influence on the trimerization outcome. Thus, the desired combination of properties cannot be achieved using the phthalate-free plasticizers described in the prior art, or can only be achieved if the TDI trimer concentration does not exceed approximately 27 wt. These adhesion promoters are either no longer processable due to their high viscosity or result in insufficient adhesive strength due to their insufficient TDI trimer concentration.

[0070] (according to the invention) 1,2-propylene glycol dibenzoate ( CAS: 19224-26-1 )

[0071] 180 parts by weight of Desmodur® T80 were trimerized at 75-80 °C in 533 parts by weight of 1,2-propylene glycol dibenzoate with 0.35 part by weight of catalyst. After 14 hours, the reaction was interrupted by adding 0.7 parts by weight of reaction stopper, and the mixture was stirred for 1 hour at 60 to 70 °C. A clear, almost colorless solution with an isocyanate content of 4.12 wt.%, a viscosity at 23 °C of 71,000 mPas, and a free TDI content of 0.46 wt.% was obtained. The viscosity was adjusted to a usable value of 8,540 mPas by adding 20 parts of 1,2-propylene glycol dibenzoate to the reaction mixture. The effectiveness was reduced by 13%, thus remaining at a high level.

[0072] Application-related testing and test results:

[0073] In a realistic test system, polyester fabric was coated with a PVC plastisol / adhesion promoter coating. The adhesion strength of this coating was then determined using a standardized test strip. For this purpose, polyester fabric was coated with an adhesive coating containing an adhesion promoter using a doctor blade. These coatings were gelled in a thermal oven and subjected to further testing. To test the adhesion strength, two test strips (PVC side to PVC side) were placed on top of each other, pressed together at low pressure and 180°C, and tested using a tensile tester. Test equipment:

[0074] Scale: Accuracy min. 0.1 g

[0075] Stirrer: high-speed rod stirrer

[0076] Mathisofen Labcoater from Mathis AG Zurich

[0077] Tractor Ametec LR5 K plus

[0078] Polyester fabric: Polyester 1100 dtex L 9 / 9 Z 60 standard fabric

[0079] Fabric samples measuring approximately 40 x 25 cm were used for the test.

[0080] Composition of PVC plastisol:

[0081] 70 T pastes PVC; Vestolit® B 7021 Ultra; Vestolit GmbH; Marl

[0082] 30 T pastes PVC Vestolit® E 7031; Vestolit GmbH; Marl

[0083] 33 T ASEP plasticizer Mesamoll®; Lanxess Deutschland GmbH

[0084] 33 T DI NP plasticizer Vestinol® 9; Evonik Oxeno GmbH, Marl

[0085] 10 T chalk Durcal® 5; Omya GmbH; Cologne

[0086] 2.5 T stabilizer Baerostab® UBZ 780 RF; Baerlocher GmbH; Berlin

[0087] 1.5 T titanium dioxide Kronos® 2220; Kronos Titan GmbH; Leverkusen

[0088] (T= parts)

[0089] Test specimen:

[0090] Adhesive coat approx. 140 g / m 2 140 °C / 2 min

[0091] After coating and pre-gelling at 140 °C, the test specimens were pressed and welded at 180 °C for 2 minutes.

[0092] Dimension: 5 cm width x 25 cm length ) in thread weft direction

[0093] Testing with Ametec LR5 K plus tractor

[0094] To produce the PVC plastisol, the starting materials listed above under "Composition of PVC plastisol" were mixed in a Drais mixer for 2.5 hours at maximum speed, with water cooling and under vacuum. Tensile test:

[0095] The adhesive strengths of these samples were then determined using a Lloyd M 5 K tensile tester. The resulting adhesive strength values ​​indicate the force in Newtons required to peel 5 cm of the coating from the carrier fabric (peel test, tabulated as effectiveness in N / 5 cm). The values ​​given in the table were obtained by averaging at least three individual measurements.

[0096] Comparative examples and inventive example

[0097] As the measurement results of Example 1 show, the phthalate-free composition according to the invention, when used as an adhesion promoter, delivers higher adhesion values ​​than those achieved with the phthalate-containing composition of the prior art (Comparative Example 1). The adhesion promoters from Comparative Examples 3, 5, and 6 were unsuitable for further processing because they were either too viscous or led to precipitates. The compositions according to Comparative Examples 4 and 5 also exhibited an unfavorable yellow coloration. It was also unexpected that only the 1,2-propylene glycol dibenzoate according to the invention from the dibenzoate class of substances showed unexpectedly good effectiveness; the other two products from this class either showed precipitates or were far too volatile.

[0098] Test results:

Claims

1. Compositions comprising: a) isocyanurates containing isocyanate groups and b) alkylenediol dibenzoate, wherein the weight ratio of a) to b) is in the range from 1:1 to 1:8, preferably from 1:1.2 to 1:4 and particularly preferably from 1:1.5 to 1:2.

5.

2. Compositions according to claim 1, wherein the alkylenediol dibenzoate has as alkylene group a branched or unbranched C2 to Cw alkylene group, preferably a branched or unbranched C2 to Ce alkylene group.

3. Compositions according to claim 1 or 2, wherein the isocyanate group-containing isocyanurates are obtainable by trimerization of a mixture containing 2,4-diisocyanatotoluene and 2,6-diisocyanatotoluene, preferably a mixture of 65 to 95 wt.% 2,4-diisocyanatotoluene and 5 to 35 wt.% 2,6-diisocyanatotoluene, wherein the weight percentages are in each case based on the total amount of diisocyanatotoluenes.

4. Compositions according to one or more of claims 1 to 3, wherein the total proportion of components a) and b) in the mixture is at least 50% by weight, preferably at least 75% by weight, particularly preferably at least 85% by weight, very particularly preferably at least 92% by weight, and most preferably between 95 and 100% by weight.

5. Compositions according to one or more of claims 1 to 4, containing, based on the total mass of the composition, up to 50% by weight of one or more diluents, preferably one or more diluents selected from the group consisting of alkyl acetate, preferably butyl acetate, ethyl acetate, propyl acetate, N-alkylpyrrolidone, N-octylpyrrolidone, N-decylpyrrolidone, DMF, acetone, paraffins, white oils, and low-aromatic aliphatics.

6. Use of compositions according to one or more of claims 1 to 5 as adhesion promoters for coating compositions based on plasticized polyvinyl chloride.

7. Use according to claim 6, wherein the coating agent contains at least one PVC plastisol.

8. Use according to claim 5 or 6, for the production of substrates with coatings containing or consisting of plasticized polyvinyl chloride.

9. Use according to claim 8, wherein the coated substrates are tarpaulins, billboards, air domes and other textile structures, flexible containers, tent roofs, awnings, protective clothing, conveyor belts, flock carpets or foam artificial leather.

10. Use according to one or more of claims 8 and 9, wherein the substrates are textiles, fabrics or leather.

11. Use according to claim 10, wherein the fabrics are textile polyester or polyamide fabrics.

12. A process for preparing the compositions according to one or more of claims 1 to 5, wherein diisocyanates are trimerized in the presence of the dibenzoate b) to the isocyanate group-containing isocyanurates a).

13. The process according to claim 12, wherein the trimerization takes place in the temperature range from 40 to 140 °C and is terminated when the content of the diisocyanates used in the reaction mixture is 0.49% by weight or less.

14. The process according to claim 12 or 13, wherein the diisocyanates used are a mixture containing 2,4-diisocyanatotoluene and 2,6-diisocyanatotoluene, preferably a mixture of 65 to 95% by weight of 2,4-diisocyanatotoluene and 5 to 35% by weight of 2,6-diisocyanatotoluene.

15. Coating agent comprising a composition according to one or more of claims 1 to 5 and at least one PVC plastisol.

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