Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-01-12
2002-09-24
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S007000, C524S008000, C264S175000
Reexamination Certificate
active
06455615
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to waterproofing materials used in construction engineering, water conservancy projects, municipal works, etc., and their manufacturing processes, especially to cement-based waterproofing materials and their manufacturing processes.
BACKGROUND OF THE INVENTION
In recent years, cement-based waterproofing materials experienced fast development and formed several product lines, such as polymer modified cement-based waterproofing membranes, rigid polymer modified cement (dry mix) waterproofing mortars, etc., among which the rigid polymer modified cement waterproofing material is the main product. The rigid waterproofing materials are modified by adding an organic polymer, a waterproofing admixture, a water reducer, and an expansion admixture to reduce and compensate for cement shrinkage, to prevent cracking, to reduce and refine the capillary pores of the materials, and to make the concrete denser and improve the impermeability remarkably. Although these materials have good aging resistance, they cannot accomodate extensive deformation of the base because of their rigidity. If dry shrinkage or expansion and contraction due to temperature changes lead to cracking of the base layer, the waterproofing layer may also crack or delaminate which will affect the waterproofing performance. Their application will be limited greatly, and they cannot be applied to large-area waterproofing engineering of floors and roofs.
In recent years, a paint with a high ratio of polymer/cement (which is about 50% by weight or higher and even up to about 100% by weight) is used as a liquid-applied membrane waterproofing material which is widely used in apartments, basements, underground water tank, etc., in Japan, Germany and some areas of China. However it needs mixing and stirring on site, and its one coating layer is thin due to the high ratios of polymer/cement and water/cement. Thus, the painted waterproofing materials need multiple coating procedures, and therefore more time and manpower are needed.
SUMMARY OF THE INVENTION
Because of the better durability and less environmental pollution during their production and application, cement-based waterproofing materials can be widely used on different base materials and are very convenient in application. A great deal of effort has been put into the studying and comparing of these materials. By improving the formulation and the production process, a polymer modified cement material with a lower ratio of polymer/cement and water/cement evenly mixed and dispersed under the impact of temperatures and high shear force can be made. It combines the advantages of a rigid cement waterproofing material with those of a flexible waterproofing material (such as rubber and plastic). Using a calendering process, a flexible cement-based waterproofing material with a denser structure, better waterproofing performance, excellent durability, and capable of accommodating deformation of the base can be obtained. Flexible is defined as capable of being bent or flexed (pliable) and further defined as being capable of being bent repeatedly without injury or damage, see
The American Heritage
®
Dictionary of the English Language
(4th ed., Boston, Houghton Mifflin, 2000).
An object the invention is to provide a process for making a flexible cement-based waterproofing material and the waterproofing materials prepared by the process.
Embodiments of the invention provide a waterproofing material, which can be used in inner, outer or concealed areas of civil engineering construction. This material can be adhered to various cement-based materials and can be used on wet surfaces during construction. Considering the advantages of the cement-based waterproofing material, the material provided in this invention is mainly cement materials.
To provide the cement-based waterproofing material, the cement material in this invention is modified by polymer dispersions, further toughened by polymers, using the processes of kneading, mixing and calendering.
The invention provides a process for making a cement-based waterproofing material, which may include one or more of the following steps:
(a) kneading a hydraulic cement and a polymer dispersion, a water-soluble polymer or a re-dispersible powder resin, or a blend thereof with water at a weight ratio of cement/polymer of 100:15-150 under conditions of about 25° C. to about 120° C., about 20 rpm to about 80 rpm, until the water content of the kneaded material reaches about 5 wt. % to about 20 wt %;
(b) mixing the kneaded material with a toughening polymer at a weight ratio of about 100:10 to about 100:50 and at a temperature of about 40° C. to about 85° C.; and
(c) rolling the resulting composition into sheets; wherein the toughening polymer is selected from rubber, thermoplastic elastomer, thermoplastic resin, or a mixture thereof.
The invention also provides a flexible cement-based waterproofing material produced by the above mentioned process. The preparation process in accordance with embodiments of the invention is described in detail in the following.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
1. Making of the Kneaded Material
In the method of this invention, the raw materials for making a kneaded material are mainly a hydraulic cement and polymers used as a modifier, the weight ratio is about 100:15 to about 100:150.
In the above raw materials, the cement should be a hydraulic cement, which may be selected from ordinary Portland cement, aluminum sulphoaluminate cement, calcium alumino ferrite cement, low alkali cement, aluminous cement, and white cement. Any of the aforementioned raw materials or a mixture thereof, or about 20% to about 50% by weight of the cement can be replaced by an equal quantity of potential hydraulic binder materials. The quantities replaced are decided according to the fineness and variety of the materials. Generally, the replacing materials are fly ash, silica fume, volcanic ash, zeolite powder, metakaolin, slag, calcium-increased liquid slag, phosphorus slag. etc. The fineness should preferably be greater than or equal to 300 m
2
/kg.
The polymers used as modifiers should meet the requirements for processing performance of the cement-based waterproofing materials and the requirements for material characteristics. They should preferably have one or more of the following advantages:
a. higher filler binding capacity;
b. good flexibility or high elasticity at application temperatures;
c. excellent anti-ultraviolet ray performance and good durability;
d. good “breathing” capability and chemicals resistance; and
e. favorable film forming temperatures and water resistance.
Any polymers that meet the above criteria can be used, for example, polymer dispersions, water-soluble polymers or re-dispersible powder resins, etc. Preferably the polymer used includes, but is not limited to, polyacrylate latex, EVA (polyethylene-vinylacetate) latex, styrene-butadiene rubber latex, chloroprene rubber latex, poly(vinyl acetate - Vinyl Versatate) latex, vinyl chloride-vinylidene chloride copolymer latex, poly(vinyl chloride-vinylacetate-acrylate) latex, polyvinyl acetate latex and re-dispersible resin powder, etc. According to the different application requirements, one may select one or more blended polymers which have suitable glass transition temperature, such as polyacrylic latex, PS9317, Tg=−40° C.; S400; Tg=−7° C.; BA163, Tg=−7° C.; P2438, Tg=−22° C.; EVA, Tg=7° C. Vinyl Versatate is a vinyl ester of Versatic acid, a synthetic saturated monocarboxylic acid of highly branched structure containing nine, ten or eleven carbon atoms.
The cement used is preferably a hydraulic gelatinous material. Through modification, the cement is hydrated and mixed with a polymer film so that the characteristics of the kneaded materials, such as waterproofing, processing and further toughening, are improved.
To further improve the kneading effect and obtain better dispersing properties, the above kneaded raw material may contain about 0.5% to
Chen Peng
Guo Yu Qing
Xia Dong
Yu Ji Guang
Zhu Lei
Jenkens & Gilchrist
Szekely Peter
Tianjin Building Materials Science Research Institute
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