Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-05-05
2001-07-31
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S048000, C524S524000, C524S315000, C239S011000
Reexamination Certificate
active
06268413
ABSTRACT:
TECHNICAL FIELD
The present invention is in the field of high-strength adhesives.
BACKGROUND
In the field of high-strength adhesives, it is desirable to produce an adhesive with a variety of beneficial characteristics.
For industrial, do-it-yourself and craft applications, it is desirable to produce a high-strength adhesive which is easily applied (typically for relatively high-volume applications). It is desirable to produce an adhesive that is spreadable and stays in place once applied. In addition, it is beneficial to produce adhesive that has good wet tack properties (i.e., having good resistance to separation of the adhered members along a vector normal to the adhered surfaces). Furthermore, it is desirable to produce an adhesive that is workable (i.e., having a practical repositioning time on the order of a few minutes) while being able to set relatively quickly to arrive at a strength sufficient to hold the substrtates or parts together to prevent separation strength (i.e., on the order of several minutes).
It is also desirable to have high-strength adhesives in a physical form that may be dispensed from open tubs or buckets through use of an application tool such as a trowel or brush, or that may be dispensed from tube- or plunger-type containers, such as syringe-type or caulk gun dispensers.
It is also beneficial to be able to produce high-strength adhesives from mixtures having a fluid consistency to allow for the use of standard mixing and dispensing equipment typically used for low viscosity products, but which set or “paste back” to a paste-like consistency allowing for ease of application. It is also desirable to have the product “paste back” within a workable time frame, allowing it to be dispensed to containers prior to arriving at its final physical form.
Another beneficial characteristic of high-strength adhesives is to be able to achieve relatively high final bond strengths with or without a static force being brought to bear (such as through clamping) to urge together the substrates to be joined.
It is also desirable to produce such high-strength adhesives in a physical form so that they reduce or prevent spillage from tipped open containers (such as tubs), or from tube- or plunger-type containers that are laid open on their sides. In the case of plunger-type containers, such as syringe-type or caulk gun dispensers, it is also desirable to be able to use high-strength adhesives that are of a sufficiently colloidal consistency that unused portions may be withdrawn into the dispenser once extruded, to avoid waste through over-application and spillage.
Another desirable characteristic in a high strength adhesive is the ability to be used on a wide variety of porous substrates including cloth and similar materials, without bleed-through of wetness.
From the following disclosure or through practice of the invention, other advantages may become apparent.
SUMMARY OF THE INVENTION
The present invention includes a high strength adhesive and includes a dispenser containing a high strength adhesive.
In broadest terms, the present invention is an adhesive composition comprising:
(a) water present in an amount of from about 40 percent to about 70 percent by weight;
(b) polyvinyl acetate present in an amount of about 15 percent to about 35 percent by weight; (c) dextrin present in an amount from about 5 percent to about 35 percent by weight; and (d) starch present in an amount from about 0 percent to about 5 percent by weight; the adhesive having at least 30% by weight solids, having a paste-like consistency, and having a bond strength greater than about 2000 p.s.i. as measured by ASTM D-905.
When pasted back, the adhesive has a very workable consistency that is very difficult to measure, but is very much like room-temperature butter or shortening used in cooking.
When freshly made (prior to pasting back), the adhesive of the present invention has an initial viscosity greater than 750 centripoise, and typically approaching about 3,000 centripoise, as measured by a Brookfield Model LV #4 spindle at 60 RPM at 35° C. (designated herein as “LV/4/60RPM”).
The polyvinyl acetate may be in the form of a dispersion in water (preferably 55% solids in water), referred to herein as P-571 (stabilized with polyvinyl alcohol). As alternatives, a vinyl acetate homopolymer, stabilized with hydroxyethylcellulose and sold under the name Fulatex® by H. B. Fuller Company of St. Paul, Minn., may also be used, as well as a dextrin-stabilized polyvinyl acetate sold under the name Rhoplex 6215 from the Rohm & Haas Company of Philadelphia, Pa. It is most preferred that the polyvinyl alcohol content, where used, should be maintained at a level no more than that needed to protect the polyvinyl acetate dispersion (typically no more than that contained in the commercially supplied product).
The dextrin used in the present invention may be from any appropriate dextrin source. Preferably the dextrin is high-viscosity potato dextrin. An example is Avedex W 15, commercially available from AVEBE of Foxhol, Holland.
The starch used in the present invention may be from any appropriate starch source. Preferably the starch is a raw, unmodified starch, preferably raw cornstarch. An example is Amaizo 100 starch, commercially available from American Maize-Products Company of Hammond, Ind.
The adhesive composition of the present invention may optionally include at least one water-soluble polymer, such as those selected from the group consisting of cellulose polymers and cellulose gums, including hydroxymethylcellulose, hydroxyethylcellulose and carboxymethylcellulose, hydroxyethylcellulose being preferred; and natural gums (e.g., xanthan gum). Examples of these materials are those sold under the names NATROSOL®, preferably NATROSOL® 250 HHXR (hydroxyethylcellulose; commercially available from Aqualon Company), METHOCEL® (hydroxymethylcellulose) and ETHOCEL® E4M (hydroxypropyl methylcellulose; commercially available from Dow Chemical Company), cellulose gum (sodium carboxymethylcellulose; commercially available from Aqualon Company, and under the name Hercules® commercially available from Hercules Incorporated).
The adhesive composition of the present invention may optionally include at least one water-soluble plasticizer for the starch derivatives and/or the water-soluble-polymer(s), such as glycerin, sorbitol, corn syrup, other sugars, and propylene glycol. The adhesive composition of the present invention also may optionally include at least one water-insoluble plasticizer for the polyvinyl acetate, such as Benzoflex® 9-88 (dipropylene glycol dibenzoate; commercially available from Velsicol Chemical Corporation of Rosemont, Ill.), Santicizer 160 (butyl benzyl phthalate; commercially available from Monsanto of St. Louis, Mo.).
The adhesive composition may also include agent(s) to impart water resistance, such as glyoxal. An example is Glyoxal 40, commercially available from Hoechst/Celanese Corporation.
Other optional components include preservatives that may be selected from any appropriate composition, such as para-hydroxyethylbenzoate (ethyl paraben; commercially available from Van Dyk Division of Mallinkrodt, Inc. of Belleville, N.J.; or microbiocides, such as Amerstat® 251, commercially available from Ashland Chemical Company of Boonton, N.J.; or Kathon LX 1.5%, commercially available from Rohm & Haas.
A defoaming composition, such polypropyleneglycol, may also be used in a preferred embodiment. An example of this component is Polypropylene Glycol 1200, commercially available from Ashland Chemical Company.
The adhesive composition may also contain dyes or other colorants that may be used to indicate adhesive type such as would glue or craft glue. These will typically be used in amounts on the order of thousandths of a percent so as to have no effect on the other desirable characteristics of the adhesive.
In a preferred embodiment, the adhesive composition of the present invention comprises: (a) water present in an amount of from about 50 percent to about 60 percent by weight; (b) polyvinyl acetate pres
Columbus Peter S.
Patel Yogeshbhai B.
Acquah Samuel A.
Elmer's Products, Inc.
Rajguru U. K.
Standley & Gilcrest LLP
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