Abstract:
A thickening agent which is based on at least one synthetic phyllosilicate which contains at least one additive from the group of organic phosphorus compounds comprising the following: 
     a) phosphonic acids with formula ##STR1## b) phosphinic acids with formula ##STR2## c) thiophosphinic acids with formula ##STR3## d) diesters of phosphorous acid with formula HO--P(OR) 2  e) diesters of phosphoric acid with formula ##STR4## f) diphosphonic acid with formula ##STR5## in which R is an alkyl or hydroxyalkyl group with 1 to 22 C atoms or an aryl or hydroxyaryl group with 6 to 12 C atoms and R&#39; is an alkylene group with 2 to 22 C atoms.

Description:
BACKGROUND OF INVENTION 
     The invention relates to thickening agents based on at least one synthetic phyllosilicate. 
     In liquid or flowable coating systems, such as paints, varnishes, adhesives, printing inks, undersealing compositions, drilling fluids, cosmetic and pharmaceutical formulations, phyllosilicates are used to solve a number of problems such as settling of heavy pigments or active agents during storage, making available the necessary layer thickness for protective reasons, making available the viscosity suitable for the particular application, etc. 
     These phyllosilicates can form thixotropic &#34;house-of-card&#34; structures which impart the desired properties to the systems. Since these products themselves have a strong thickening action, which is certainly the reason for their use, the materials are not offered or marketed in predispersed form. This is due mainly to the fact that only pastes having a solids content of 2 to 8% can be produced and handled as a suspension. With the product essentially comprised of water, transportation of the product is not economically feasible. 
     Moreover, too much water can be brought into the formulation. This can result in the desired thickening effect of the phyllosilicate being neutralized by the high additional amount of water. 
     Moreover, a good dispersion of powders is a problem with phyllosilicates. Either the dispersion is not complete and the material is only partially used, (this also leads to other problems such as seeds (coarse particles) formation, post-thickening phenomena, loss of gloss and efficiency), or the dispersion is not possible in the desired formulation as the result of a lack of water and thus the possibility of compensating for the lacking mechanical dispersion forces by swelling with water. Even if the necessary mechanical dispersion energy is available, in many cases dispersion cannot be completely effected, as the components of the formulation are not always shear-stable. Uncontrollable post-thickening effects are thus the result and in some circumstances also seed formation, agglomerates and loss of gloss. 
     The addition of dispersion agents to improve dispersion is known in the art. However, this addition is normally done only after the phyllosilicate has been prewetted in water. The phyllosilicate is generally prewetted because most dispersion agents are highly polar and thus, can become attached to the edges of the phyllosilicate lamellae, such that hydration is suppressed and the opposite effect from dispersion is achieved. Dispersion agents, for example, based on acrylate or acrylamide, have a tendency to flocculate suspensions. This naturally reduces the viscosity of a phyllosilicate gel and also results in poor delamination and dispersion. 
     A process for producing organophilic clays with improved dispersibility in organic liquids is known from U.S. Pat. No. 4 382 868, in which a mixture of a smectite clay, a quaternary ammonium or phosphonium compound, water and an alcohol with 1 to 5 carbon atoms is extruded and the resulting organoclay gelatinization agent is ground without removing the water or alcohol. The product is no longer a clay which is capable of swelling in water. 
     A flame-inhibiting lubricant is known from U.S. Pat. No. 5 128 067 which contains a mixture of alkoxy and phenyl triesters of a phosphorus oxy acid and a fine-particle silica-containing thickening agent, for example, clay and silica. However, it is not a conversion product. 
     Organophilic clays are known from U.S. Pat. No. 5 336 647 which discloses the reaction product of a smectite clay with a first organic cation and a second organic cation from a polyalkoxylated quaternary ammonium salt. The clay is no longer present in hydrophilic form. 
     A gel-forming organophilic clay is known from DE-C-3 145 452 which discloses the reaction product of a clay of the smectite type with an organic anion (for example, a phosphite or phosphate) and an organic cation, for example, a quaternary ammonium or phosphonium compound. The conversion product is no longer hydrophilic. 
     An agent for enhancing the viscosity in nonaqueous liquid phases is known from DE-A-3 914 916 which is formed from finely dispersed particles of an inorganic laminar compound with positive layer charge based on two dimensional inorganic polycations (polycationic laminar compounds) and mono- and/or polybasic acid anions of a pronounced oleophilic nature. This product is not capable of swelling in water. 
     A gel-forming organophilic clay is disclosed in DE-A-3 145 475, which represents the reaction product of an organic cation, an organic anion and a clay of the smectite type. The organic cation is chosen from the group of quaternary ammonium salts, phosphonium salts and/or sulfonium salts. This product is not capable of swelling in water. 
     Use of phosphoric acid esters and their salts as dispersion agents and dispersion stabilizers for pigments in dyes, paints, and synthetic resins is known from DE-A-3 930 687. Aluminum hydroxide, zinc stearate, calcium carbonate, magnesium oxide and carbon black are named as pigments. 
     Easily dispersible organosmectites are known from DE-C-3 230 476 which contains exchangeable cations which have been replaced up to 50% by organic cations and which contains a surface which is covered with a peptising agent which is chosen from the group of sodium tetrapolyphosphate, sodium tripolyphosphate, sodium silicate, pyrogallol, gallic acid, and tannate. This product is also no longer capable of swelling in water. 
     It is known from Kittel, Hans: Lehrbuch der Lacke und Beschichtungen (Textbook of Paints and Coatings), Verlag W.A. Colomb in H. Heenemann GmbH, Berlin-Oberschwandorf, 1974, volume II, pp. 340, 341 that silicates, for example, minerals of the montmorillonite type, can be used as additives for paints. No information is disclosed on the modification of these substances for purposes of better dispersibility. 
     Rheological additives or thickening agents for pigment-containing protective coatings are known from Van Doren, Robert E., et al.: &#34;The Role of Rheological Additives in Protective Coatings&#34;; Journal of Protective Coatings and Linings, May 1989, pp. 47-52. Among those disclosed are pyrogenic silicic acids, cellulose-containing thickening agents, acrylates, and polyester-polyurethanes. 
     The objective of the invention is therefore to improve the dispersibility of phyllosilicates such that a powdered material can be easily dispersed at low to medium shearing forces without seeds. Another object is to provide pumpable pastes which can be easily metered and in which the phyllosilicate is present in completely dispersed form. 
     SUMMARY OF INVENTION 
     The subject matter of the invention is a thickening agent based on at least one synthetic phyllosilicate which is characterized by the fact that it contains at least one additive from the following group of organic phosphorus compounds: 
     a) phosphonic acids with formula ##STR6## 
     b) phosphinic acids with formula ##STR7## 
     c) thiophosphinic acids with formula ##STR8## 
     d) diesters of phosphorous acid with HO--P(OR) 2   
     e) diesters of phosphoric acid with formula ##STR9## 
     f) diphosphonic acids with formula ##STR10## in which R is an alkyl or hydroxyalkyl group with 1 to 22 C atoms or an aryl or hydroxyaryl group with 6 to 12 C atoms and R&#39; is an alkylene group with 2 to 22 C atoms. 
     DESCRIPTION OF THE INVENTION 
     Surprisingly it was found that by using the thickening agents according to the invention, the dispersion problems previously discussed can be solved. These novel products can be dispersed either as powders directly into the finished formulation without seeds or as pumpable pastes with the viscosity of these thickening agents in water reduced. In addition, highly concentrated pastes can be produced without the efficiency of the thickening agent in the system being impaired. 
     It is also possible by means of the thickening agents according to the invention to subsequently work powder into the finished systems without applying extreme shear forces. 
     The subject matter of the invention is also a process for producing a thickening agent according to the invention, addition being done either 
     (a) as powder to the dry powder of the phyllosilicate; or 
     (b) in dissolved form as a liquid at a suitable stage in the synthesis of the phyllosilicate, preferably to the filter cake. 
     The subject matter of the invention is also a master paste which is produced from the thickening agent according to the invention and which contains up to 35% by weight, preferably 5 to 25% by weight, especially 10 to 20% by weight solid. 
     The subject matter of the invention is also the use of the thickening agent according to the invention or master paste in liquid or flowable coating systems, i.e., which can be applied by coating, spraying, rolling etc., such as for example paints and varnishes, cosmetic and pharmaceutical preparations (such as creams and toothpastes), fertilizer suspensions, pesticide spray systems, undersealing compositions, bitumen emulsions, lubricating greases, polishing agents, printing inks, structural plasters, etc. With this product the rheology can be adjusted, in particular, its viscosity, stability (anti-settling effect, syneresis) and layer thickness (anti-sagging action). 
     The invention is detailed by the following examples. 
    
    
     EXAMPLES 
     Example 1 
     Three percent by weight of a synthetic hectorite was dispersed in 97% by weight demineralized water. For comparison, 3% by weight synthetic hectorite was dispersed in demineralized water with 1% by weight of additives listed below in Table I, relative to the amount of hectorite added (=0.03% of the total amount). The viscosity in the dispersion was measured in mPa.s (Viscolab LC 10, Physica). 
     The results are given in Table I. 
     
                       TABLE I______________________________________Thickening               Viscosityagent   Dosage  Additive     Dosage                              1 h   24 h______________________________________synthet.   3%      0            0     18500 26000hectoritesynthet.   3%      Na-polyphosphate                        1%    16300 32000hectoritesynthet.   3%      Na-polyacrylate                        1%    12000 20000hectoritesynthet.   3%      Hydroxyethane-                        1%    4200  9200hectorite       1.1-di-           phosphonic acid______________________________________ 
    
     Example 2 
     A 3% gel of synthetic hectorite was produced in demineralized water analogously to Example 1. In comparison, gels with 3% by weight of the additives listed below (0.09% of total amount) were produced. 
     The viscosity of the gels is given in Table II. 
     
                       TABLE II______________________________________Thickening               Viscosityagent   Dosage  Additive     Dosage                              1 h   24 h______________________________________synthet.   3%      0            0     11700 19000hectoritesynthet.   3%      Na-polyphosphate                        3%    9000  15000hectoritesynthet.   3%      Na-polyacrylate                        3%    5800  10600hectoritesynthet.   3%      Hydroxyethane-                        3%    4     4hectorite       1.1-di-           phosphonic acidsynthet.   3%      Na-phosphonate                        3%    2760  6800hectorite______________________________________ 
    
     The results of Examples 1 and 2 show that the organic phosphorus compounds according to the invention reduce the viscosity of dispersions much more than conventional dispersion agents based on Na-polyphosphate or Na-acrylate. It is also recognizable that by increasing the amount added from 1% to 3% of the additive, the liquefying action is intensified. 
     Example 3 
     Synthetic hectorite from Example 1 was dispersed in demineralized water (dissolver, 5 minutes, 2800 rpm, from Pendraulik) and the viscosity of the gel obtained was measured in mPa.s after 1 h or 24 h in a Brookfield DV-II. 
     In comparison, the synthetic hectorite was mixed with the sodium salt of hydroxyethane-1,1-disphosphonic acid, homogenized and dispersed in demineralized water. 
     The results are listed in Table III. 
     
                       TABLE III______________________________________% of                  Dosagesynth.     % of       in      Viscosityhectorite  additive   water   1 h    24 h______________________________________a)    100%     0%         4%    10600  19800b)    100%     0%         6%    56500  81700c)     96%     4%         8%    6      6d)     94%     6%         25%   1260   96______________________________________ 
    
     Example 4 
     Synthetic hectorite was mixed with phosphonic acid (Sapetin D100 from Woellner) or with Na-polyphosphate, homogenized, and dispersed in demineralized water analogously to Example 3. The viscosity was measured in a Viscolab LC 10 from Physica. 
     The results are listed in Table IV. 
     
                       TABLE IV______________________________________% of                    Dosagesynth.                  in       Viscosityhectorite  % of additive                   water    1 h   24 h______________________________________a)   100%      0%           4%     10600 19800b)   100%      0%           6%     56500 81700c)   94%       6% Phosphonic                       6%     24600 42500          acidd)   94%       6% Na-       6%     16800 28300          polyphosphatee)   94%       6% Phosphonic                       4%     6600  12600          acidf)   94%       6% Na-       4%     2060  7080          polyphosphate______________________________________ 
    
     Example 5 
     Analogously to Examples 3 and 4, the synthetic hectorite was homogeneously mixed with additives and a gel produced in tap water with the mixed product (stirred in the dissolver for 5 minutes at rpm) and the viscosity was measured (Viscolab LC 10) 
     The results are given in Table V. 
     
                       TABLE V______________________________________% of                    Dosagesynth.                  in       Viscosityhectorite  % of additive                   water    1 h   24 h______________________________________a)   100%      0%           4%     35800 77600b)   100%      0%           6%     85300 163700c)    94%      6% Phosphonic                       4%     5420  7800          acidd)    94%      6% Na-       6%     17100 25900          polyphosphate______________________________________ 
    
     Examples 4 and 5 clearly show that the viscosity, mainly in tap water, can be reduced by adding standard dispersion agents. The liquefying action of the additive according to Example 3 however is not reached by far. 
     Example 6 
     As the viscosity of the master pastes, i.e., the thickening agents dispersed in water, is greatly reduced by the additives, it remains to be demonstrated that the thickening agent does in fact develop its effectiveness even in the finished system, as, for example, a paint. 
     This was tested with the following decorative paint (guideline formulation C-823 from ICI): 
     
         ______________________________________Formulation:    Propylene glycol                    5.50    parts by weight    Water           7.75    parts by weight    AMP-95 ®    0.50    parts by weight    Dehydran 1293 ®                    1.25    Surfynol 104 E ®                    1.00    Neocryl BT-24 ®                    7.25    TiO.sub.2 (Tioxide TR-92)                    56.25______________________________________Dispersion to &lt;10 micronsWater           8.50Neocryl AH-24-C ®           25.00     3 min, 930 rpmRheol. add. see Table VI           x         10 min, 3720 rpmNeocryl AH-24-C ®           113.75    5 min, 930-2800 rpmDiethylene glycol           15.50     5 min, 930-1865 rpmDehydron 1293 ®           2.25Byk 154 ®   1.75      5 min, 930-1865 rpm______________________________________ 
    
     
                                           TABLE VI__________________________________________________________________________             AmountSynth.            added in                   Viscosity                        Grain                            Gloss                                Sag athectorite  % of additive             formulation                   mPa.s                        micron                            60°&lt;                                micron__________________________________________________________________________a)  100% --         0.9%  144  100 54.3                                150b)  95%  5% Na-polyphosphate             0.9%  188  50  50.5                                150c)  95%  5% Phosphonic acid             0.9%  415  100 52.2                                175d)  95%  5% Hydroxyethane-1-             0.9%  2841 40  62.2                                300  1-diphosphonic acid__________________________________________________________________________ Working-in took place as a powder. Primarily example (d) shows the outstanding effect of the thickening agent in the system. 
    
     Example 7 
     The action of the homogenized mixed products was also checked in a commercial, water-dilutable acrylic radiator paint. In this purchased paint (commercial product of Sudwest Lacke &amp; Farben) the thickening agent was worked in as a powder (in the dissolver, 15 minutes stirring, 2800 rpm). 
     Radiator paint undiluted: 1700 mPa.s 
     Gloss (60°&lt;) : 79 5 
     
         ______________________________________                  AmountSynth.                 added to        Glosshectorite  % of additive   paint    Viscosity                                  60°&lt;______________________________________100%   --              2%       58,200 42.594%    6% hydroxyethane                  2%       98,400 57.8  diphosphonic acid-  Na-salt94%    6% Na-polyphosphate                  2%       55,500 49.194%    4% hydroxyethane                  2%       89,600 55.2  diphosphonic acid-  Na-salt98%    2% hydroxyethane                  2%       85,200 47.0  diphosphonic acid-  Na-salt______________________________________ 
    
     Example 8 
     The rheological additives according to the invention were also tested in a wood preservative stain in the following formulation. 
     
         ______________________________________Parts by Weight______________________________________Water           9.4Rheol. add. see Table VIII           20.0   as 4% pre-gel in waterLumiten in RBD ®           0.4    10 min, dissolver, 930 rpmPigment distributor A ®           0.4Acronal A 627 ®           136.0Agitan 702 ®           0.8Propylene glycol           10.0Solvenon PP ®           4.0    10 min, 930 rpmMergal S 96 ®           6.0Luconyl-water paste ®           10.0   5 min, 930 rpm______________________________________ 
    
     
                       TABLE VIII______________________________________Synth. % of       Dosage in Viscosity                              Grain Shinehectorite  additive   formulation                       mPa.s  micron                                    60°&lt;______________________________________100%   --         0.4%      153    100   38.894%    6% Na-poly-             0.4%      175    90    60.6  phosphate94%    Hydroxy-   0.4%      148    15    75.7  ethane-1.1-  diphosphonic  acid______________________________________ 
    
     Examples 6 through 8 clearly show that the rheological thickening agents which were modified from a synthetic phyllosilicate by adding an additive have an outstanding effect in coating systems. In spite of the &#34;liquefaction&#34; (viscosity reduction) of the parent paste, which is to some extent very dramatically pronounced, the action was preserved in the system or the action became even better in comparison to the unmodified version.