Water Repellent and Preservative for Wood Products

This invention relates to a water repellent and preservative for cellulose material such as wood, and in particular to an emulsion concentrate containing 3-iodo-2-propynyl butyl carbamate and designed for use by addition of water to provide an aqueous solution for impregnating the wood or other material.

Clean, penetrating, paintable solvent-based water repellent and preservatives for wood have been commercially available since the mid-1930's. These combined water repellent and preservatives are the most widely used products today for the protection of millwork items, shingles, siding, flooring, structural lumber, underlayment, sheathing, plywood, fences, outdoor furniture and other wood or wood-based products that must be protected from decay, staining organisms and wood destroying insects. These products are light-bodied, penetrating solutions that leave no perceptible surface coating, impart little or no color, are free from odor and make an excellent base for paint, varnish, enamel, stains, caulks and/or glazing compounds.

The water repellents reduce the natural affinity wood has for water. Wood splitting, end checking, and grain raising are minimized and service life of wood and finish is increased. Because of the penetrability of the product adequate protection can be obtained for above ground exposure, by brush application, flood coat, dip or long cold soak.

Although these organic solvent-based products have been successfully used for over 40 years their future is now in doubt. Clean air legislation will restrict and limit the use and discharge into the atmosphere of many solvents. Costs are escalating for solvents and freight. Insurance rates and fire hazards are greater when a flammable and combustible solvent is used. Pentachlorophenol, the principle fungicide used in current water repellent preservative formulations is undergoing review by the Environmental Protection Agency to determine if it should continue to be registered as a pesticide for treating wood. There is a need for a new generation of products that will eliminate the deficiencies of current solvent-based products yet retain the many desirable characteristics.

Accordingly, it is an object of the present invention to provide a new and improved water repellent preservative for wood which eliminates the undesirable features of the products currently in use. A further object is to provide such a material which can be used with various cellulose materials including paper, hardboard, particleboard, fiberboard, plywood, solid wood and some other materials.

Many preservative chemicals are effective when used alone, but are not compatible with other components that are needed to formulate a water repellent product which can be prepared in concentrate form and utilized by simple dilution with water to produce a ready-to-use aqueous solution.

It is a particular object of the present invention to provide a new and improved water repellent and preservative incorporating 3-iodo-2-propynyl butyl carbamate in an emulsion concentrate which can be diluted with water at the point of use to provide a ready-to-use water repellent preservative.

Desirable features of such material include: water based, requiring no organic solvents; stable both as a concentrate and after dilution in ready to use form; can be sold as a concentrate to save on storage and shipping costs; nonflammable both in the concentrate and ready to use form; low toxicity to animals and humans in both concentrate and ready to use form; effective in dimensionally stabilizing wood to minimize end checking, grain raising, splits, checks and other forms of degradation; contains a preservative effective to provide protection against staining and decay organisms and mildew and molds; results in a treated wood product which is paintable and receptive to adhesives, caulks and glazing compounds with no detrimental effect on color or appearance of applied finishes; vapors which are non-toxic and have low odor; biodegradeable but not chemically broken down when exposed to the sun, while having good heat resistance; and meets the performance requirements of Industrial Standard IS-4 (NWMA) and Federal Spec. TT-W-572B.

It is an object of the present invention to provide a new and improved material which has the features set out above.

Other objects, advantages, features and results will more fully appear in the course of the following description.

The present invention includes a method of protecting cellulose materials such as wood by impregnating the material with an aqueous solution containing 3-iodo-2-propynyl butyl carbamate.

The invention also includes a combined water repellent and preservative emulsion concentrate suitable for dilution in water and treatment of cellulose material such as wood by impregnating the wood with the diluted concentrate. The invention also includes the method of treating the cellulose material with the concentrate including the steps of diluting the concentrate and impregnating the wood with the resultant solution.

A particular feature of the invention is the production and use of a concentrate containing a water insoluble active ingredient 3-iodo-2-propynyl butyl carbamate dispersed in a latex and wax emulsion to produce a stable homogeneous concentrate which can be diluted with water at the point of use to provide the water repellent preservative for wood which can be applied by brush, flood spray, immersion, soak, vacuum, pressure or otherwise as desired.

Many preservative chemicals presently available are effective when used alone, but are not compatible with other materials that are needed in a finished product to provide a concentrate for use as a water repellent and preservative for wood or other cellulosic materials. The present invention utilizes as the active preservative, 3-iodo-2-propynyl butyl carbamate, incorporating this material in high concentration with water repellent material which after processing are readily dilutable with water to provide an easily applied water repellent preservative. Some raw materials in such a product tend to mask the effectiveness of the fungicide. In the present invention, the selection of raw materials and the sequence in which they are combined is important in producing an emulsion of water repellent and preservative ingredients resulting in a solution which is stable at low and high temperatures and over a broad range of pH with no separations.

The constituents and the range of each in percent by weight for the 1+4 concentrate are set out in Table 1.

Other suitable materials for the vehicle and binder (2) are polyvinyl acetate, vinyl acetate acrylic copolymer, and ethylene vinyl acetate. Other suitable materials for the stabilizers and coupling agent (3) are propylene glycol, and polyethylene glycol with a molecular weight range of 200-400. Other suitable materials for the thickener (6) are algin derivatives, guar gum derivatives, xanthan gum, hydroxy ethyl cellulose with a molecular weight range of 4,000-30,000, and carboxy vinyl polymer.

A typical formula in percent by weight to produce a concentrate suitable for dilution with the ratio of concentrate to water of 1+4 is set out in Table 2. For every one volume of concentrate, four volumes of water are added making five volumes of ready to use material. After mixing of concentrate and water, the material is applied to the wood by any of the conventional processes, including brushing, flood coating, dipping, long soak, and the like. While a 1+4 ratio of concentrate to water is presently preferred, concentrates may be produced for use with ratios of 1+1 to 1+6.

The functions of the various constituents are set out in Table 3.

The presently preferred procedure for producing the concentrate is set out in Table 4.

The procedure of Table 4 will yield a product having the following specifications:

A ready to use product is produced by adding four parts water to one part of the concentrate of Table 4, which has the following specification:

The ready to use product has the following characteristics in use:

The product is freeze-thaw stable, non-flammable, easy to dilute at ambient conditions with a minimum of agitation, and stable in the dip tank after treating wood. The product does not introduce solvents in the system to cause wet back, nor discharge solvents on drying, and has low toxicity (Oral LD 50 1/10 Penta.). The product imparts little or no color change on wood, the treated wood has no residue odor, there is reduced penetration in blue stained or "sinker" stock, and the treated wood is non-corrosive. The product meets existing air pollution laws, is not hazardous to the environment, and produces no bloom.

The product of Table 2, diluted with four parts water, was tested as a fungicide using a standard National Woodwork Manufacturers Association (NWMA) Soil-Block Test to determine and compare effectiveness with a Standard Solvent Based 5% Penta treating solution. This test method is used to determine the minimum amount of preservative that is effective in preventing decay of selected species of wood by selected fungi under optimum laboratory conditions.

The test method may be briefly summarized as follows: Conditioned blocks of wood are impregnated with solutions of a preservative in water or organic solvent to form one or more series of gradient retentions of the preservative in the blocks. After periods of weathering, the impregnated blocks are exposed to the wood-destroying fungus, Lenzites trabea (Madison strain 617). The minimum amount of preservative which protects the impregnated blocks against decay by the fungus is defined as the threshold retention for that organism. Failure to protect is evidenced by loss of wood from the treated wood blocks, as indicated by a loss in weight.

The threshold retention expressed in pounds of treating solution per cubic foot of wood represents the minimum amount of preservative necessary to protect wood from decay. The threshold concentration is defined as the percent preservative in a given treating solution required to treat wood at a given retention to prevent decay. The use concentration as stipulated by the NWMA is 5.4 times the threshold concentration.

The table 2 product when diluted 1+4 to the ready-to-use state contains 0.105 lbs 3-Iodo at 40% activity or 1.05.times.0.40=0.042 lbs. active 3-Iodo. ##EQU1##

NWMA requires 0.27% active 3-Iodo per gallon. Hence the ready-to-use water based Table 2 product contains (0.501/0.27) or 1.85 times more than the required amount.

Toxicity tests were conducted on the 1+4 concentrate of Table 2 with the following results:

ACUTE DERMAL LD 50:

Greater than 2.0 Ml/KG of body weight. In accordance with FHSA regulations, this material is not considered toxic by the dermal route of administration.

ACUTE INHALATION:

The test material, where aerosolized, produces particles of which 90% are greater than 100 microns in accordance with EPA guidelines, inhalation testing of this product is not required. (Materials which produce 80% or more particles greater than 10 microns in diameter does not require inhalation toxicity to support registration.)

AVIAN LD 50:

(Bobwhite Quail) is in excess of 2000 mg/kg of body weight.

DERMAL SENSITIZATION:

Based on the results obtained, this material is not considered as skin sensitizer.

ACUTE ORAL LD 50:

Greater than 5.0 Ml/KG of body weight for both male and female rats.

PRIMARY EYE IRRITATION:

0.0, not an eye irritant.

CHOLINESTERASE INHIBITION SCREEN:

The test sample (1+4 conc) 5 ml/kg of body weight caused significant decrease in the RBC cholinesterase activity in two hours after administration in male rats and in four hours after administration in female rats. The cholinesterase activity returned to normal within 24 hours after administration.

The test sample contained compounds that caused inhibition of cholinesterase activity of red blood cells.

DAPHNIA: (Aquatic invertebrate)

EPA TOXICITY CATEGORIES:

Category I--"Danger" or "Poison"; Category II--"Warning"; Category III--"CAUTION". Woodlife (Water Based) 1+4 concentrate based on EPA's outlined toxicity tests is classified as category III, 5% Penta based products are classified as category II.

Set out below as Tables 5, 6, 7 and 8 are usable concentrate formulas with the amount of one constituent varied. Constituent 1, the water repellent, is varied in Table 5; constituent 2, the vehicle and binder, is varied in Table 6; constituent 3, the stabilizer and coupling agent, is varied in Table 7; and constituent 4, the preservative is varied in Table 8. These tables show the useful ranges of the various constituents. The optimum values and the characteristics of the extremes are discussed in the notes following each table.