JPS6335744B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an adhesively bonded nonwoven web having a predominant amount of papermaking fibers and containing a ternary polymer adhesive for the fibers of the web, and borate ions for pre-wetting the web. The present invention relates to a pre-humidified wiper containing a water-based lotion. The lotions used in the invention contain α-hydroxy acids, o-aromatic hydroxy acids or keto acids to achieve a synergistic effect. Washable nonwoven webs and fibrous batted cotton (worsted) are constructed to have temporary wet strength. Two basic approaches have been taken to obtain temporary wet strength. One method uses polyvinyl alcohol gelled with borate ions, which decomposes in the presence of large amounts of water, but temporarily retains its strength in the presence of limited amounts of liquid. For example, all
U.S. patent number issued to D.Duchane
No. 3,645,928, US Pat. No. 3,692,725, and US Pat. No. 3,808,165. A second method to obtain temporary wet strength is to blend water-insensitive polymers with water-soluble materials.
Water-insoluble materials retard the effects of water, and water-soluble materials provide sites for the water to gradually degrade the adhesive, causing the web to disintegrate. See, eg, US Pat. No. 3,554,788 entitled "Water Dispersible Nonwoven Fabric." Such prior art methods are usually based on the presence of woven lengths of fibers in the web to provide wet strength due to long fiber lengths that entangle or rope the fibers. A multilayer method for obtaining a pre-wetted, flushable wiper is disclosed in US Pat. No. 3,881,210 and has a water-dispersible thermoplastic reinforcing layer. A fiber adhesive bonded by special enzymes to obtain dispersibility is disclosed in US Pat. No. 4,009,313. Prior art techniques for imparting temporary wet strength to webs have been known to be wetted with water-based lotions and exposed to the extreme environmental conditions that may be encountered during shipping of industrial products. They are unsatisfactory in terms of their ability to maintain their wet strength over a period of time (for example, months) and to be able to disperse them after use. The prior art loses its wet strength during prolonged contact with water-based lotions or disperses when immersed in large amounts of water after being exposed to high temperatures, e.g. 60°C (140°C). Either he would lose his ability. Furthermore,
These systems, which relied solely on the interaction between polyvinyl alcohol and borate ions in lotions, required high concentrations of borate ions, which is undesirable in lotions designed to cleanse human skin. . According to the present invention, a nonwoven adhesively bonded web containing a major amount of papermaking fibers is impregnated with a water-based lotion agent. The web is coated with at least 44.56 g/cm in at least one direction while being wetted with a water-based lotion for an extended period of time.
(4 ounces per inch) and substantially loses its wet tensile strength when immersed in water at least 10 times the weight of the web. This wet tensile strength is imparted to the web by an adhesive composition that obtains at least some of its adhesive properties through interaction with the lotion agent. and the adhesive composition, when applied to a web, comprises: (A) about 5 to about 15 parts polyvinyl alcohol; and about 0.75 to about 1.25 parts of a water-dispersible, self-crosslinking, thermosetting polymer emulsion. The water-based lotion contains an effective amount of borate along with desired lotion ingredients such as fragrance, soap or preservatives and is adjusted to a pH ranging from about 8 to about 10. . Additionally, nonwoven webs bonded with polyvinyl alcohol have synergistic wet strength and dispersion properties when the lotion contains a type of organic acid capable of complexing with borate along with borate ions. to improve. The impregnated wiper web component contains a predominant amount of short fibers and is a dry formed web or a non-wet reinforced, wet laid paper web. Dry-formed webs are made by slurrying fibers in water.
It is a type of nonwoven material made by methods other than the typical wet papermaking process, in which the fibers are deposited on a porous surface through which water passes to form a web. Dry molding methods do not use water and fiber slurry, and therefore these methods are referred to as "dry" molding, although moisture is present during the molding process. Typical dry-formed, nonwoven fabrics suitable for this invention include air-laid webs and carded fibers, as long as they are made from a predominant amount of paper-length fibers (minor amounts of woven-length fibers may be mixed in). It's the web. Predominant amount of web fibers are papermaking length or shorter (papermaking fibers average 0.9525 cm (3/8 inch))
(or shorter), the fibers are usually wood pulp fibers, although linters and synthetic fibers such as rayon, polyester and mixtures thereof are suitable. The fibers are dispersed in the gaseous fluid and deposited on the porous surface to form a web.
The equipment that forms such webs is usually called a dry web forming machine, and the RANDO-FEEDER
and RANDO-WEBBER. Dry formed webs must be bonded to provide structural integrity and wet tensile strength to the web. The bonded web is dried to cure the adhesive. Although small amounts of moisture may be added at various points in the manufacturing process, this web is still technically referred to as "dry formed." Unless adhesives are used, the web will have little or no wet strength. Specific examples of dry formed webs and methods of making the same are provided by Norton et al., U.S. Pat. No. 3,862,472;
GB 1,311,619 and GB 1,246,910, which patents are incorporated herein by reference for their disclosures to dry formed webs and methods of making them. Wet-laid paper webs are not covered by this invention unless they contain a sufficient amount of conventional wet strength resins to give the web a wet tensile strength in any direction greater than about 4 ounces/inch. suitable for use. Such wet laid paper webs are referred to herein as non-wet reinforced paper webs.
Such a non-wet reinforced paper web, when strengthened with the adhesive composition of the present invention and wetted with a lotion agent, has a strength of 44.56 g/cm (44.56 g/cm) in at least one direction.
ounces per inch) and is dispersible in water. In general, preferred webs for practicing the present invention are made from wood pulp fibers mixed with synthetic fibers (e.g., rayon), and these fibers are suspended in air and deposited onto a porous member to form a non-woven material. A low-density mat (web) of the bond is formed and subsequently adhered in the presence or absence of moisture, embossed, and allowed to dry and cure the adhesive. Approximately 80% wood pulp (0.9525cm (3/8″) or shorter) and approximately 20% synthetic fiber (approx.
3.81cm (approximately 1.5″) long] and approximately 9.07 to approx.
A dry-formed web having a weight in the range of 20 to 110 pounds per ream, but containing an adhesive composition of the type defined below.
Scott Paper under the product name ShopTowel
Particularly preferred are webs of the type sold by Company. Web Adhesives The fibers of the web are bonded with an adhesive composition to provide web strength and structural integrity. At least about 1% adhesive is added to the web based on the weight of polymer solids in the adhesive and the weight of air-dried fibers in the web. Preferably from about 4% to about 20% adhesive is added to the web, particularly preferably 12%. Conventional methods for applying adhesive to dry-formed webs include spraying an adhesive composition onto the formed web, foaming the adhesive composition to disperse adhesive foam onto the web, and adhering to the web. Methods suitable for use in the present invention include printing the adhesive composition onto a web in a continuous or discontinuous printed pattern of discrete areas of the adhesive composition by known methods such as gravure roll printing. There is. Since the dispersibility of the web does not require any special adhesive distribution pattern, there is no need to use any special mold pattern. Preferably, the adhesive is applied uniformly over both sides of the web and penetrates into the web to effectively adhere the fibers to the web. Since most of the fibers are paper length (average length), the wet strength of the web is essentially due to adhesive bonding. Adhesive Composition The main inventive idea of the present invention is to combine the three essential adhesive components within a specific proportion for each component in combination with a water-based lotion having an alkaline PH and containing borate ions. The present invention relates to the use of an adhesive composition comprising: The adhesive composition applied to this web contains the following three components. (1) Component 1 is a cold water soluble, medium to high molecular weight, partially hydrolyzed (70% to 90% hydrolyzed) polyvinyl alcohol (PVA). The molecular weight of PVA is expressed as the degree of polymerization (DP) and is at least
450, preferably in the range of about 450 to about 2500. Such partially hydrolyzed, medium to high molecular weight PVA is readily available and known to those familiar with adhesives. This PVA is the main component of the adhesive composition and constitutes about 5 to 15 parts of the adhesive composition. For adhesive compositions, parts are parts by weight based on the total weight of polymer solids in the adhesive composition (not including the water portion). Approximately 8 parts PVA for 78% hydrolyzed PVA
It is preferred to use about 15 parts of PVA, but for about 90% hydrolyzed PVA it is preferred to use about 15 parts of PVA. 60
Neither % hydrolyzed PVA nor 99% hydrolyzed PVA will disperse (solubilize) in cold water and are therefore outside the scope of the present invention. (2) Component 2 can act as a fiber adhesive;
having a molecular weight of at least about 100,000 and about -50°C
glass transition temperature ranging from +45°C (torsion modulus of air-dried film of polymeric solids is 300°C)
A non-self-crosslinking, water-dispersible, thermosetting polymer emulsion, which is a film-forming polymer with a temperature of Kg/ ^cm2 ). The glass transition temperature is preferably -46°C to +33°C. "Non-self-crosslinking" refers to a polymer without suitable cross-linking moieties in the polymer chain for cross-linking to adjacent polymer chains, either directly or through a cross-linking agent. Such polymers are commonly referred to in the industry as non-crosslinking, or crosslinking but not self-crosslinking. This polymer is usually a polyacrylic or polyvinyl polymer or a copolymer thereof. Water-dispersible means insoluble in water, but dispersible and forming an emulsion in water with emulsifiers (surfactants). RHOPLEX is Rohm
and Haas Company, a series of suitable nonionic and cationic polymer emulsions, many of which are non-self-crosslinking. −
The first glass transition temperature (T ₃₀₀ ) of 17 °C, and 25
It has a viscosity of approximately 200 cps. (tested on a No. 3 spindle at 60 rpm on a 45% solids emulsion using a Bruckfield viscometer) at °C and is cross-linking, but non-self-crosslinking. Particularly preferred is RHOPLEXHA-4, a binding, nonionic acrylic polymer emulsion. In addition to acrylic polymers, suitable polymers include vinyl, nitrile and styrene butadiene polymers and copolymers such as ethylene vinyl acetate available from Du Pont as ELVACE 1961. This is a typical cross-linking polymer in the RHOPLEX series, but non-self-cross-linking polymers include
RHOPLEX B-15 (T ₃₀₀ = -4℃) and
There is an acrylic polymer known as RHOPLEX B-10 (T ₃₀₀ =-7°C). Component 2 is 1.5-2.5% of the adhesive composition when applied to the web.
constitute the department. (3) Component 3 is a water-dispersible, self-crosslinking polymer similar to component 2 in which the polymerization-reactive moiety that makes the polymer self-crosslinking is not introduced into the polymer. Typical reactive sites include carboxyl or N-methylolamine functional groups.
Suitable polymers have a molecular weight greater than about 100,000 and a primary glass transition temperature in the range of -50°C to +45°C, preferably in the range of -22°C to +33°C (with a torsion modulus of an air-dried film of the polymeric solid of 300°C).
Kg/ ^cm2 ). Representative self-crosslinking polymer emulsions suitable for use in the present invention as component 3 include acrylic, nitrile, vinyl and styrene butadiene polymers and copolymers thereof. A suitable self-crosslinking polymer emulsion is RHOPLEX
HA-16 (T ₃₀₀ +33℃), HA-8 (T ₃₀₀ -14℃),
and the trade name TR-520 (T ₃₀₀ -8℃)
A series of self-crosslinking acrylic polymers are available from companies such as Rohm and Haas Company. Ethylene vinyl acetate self-crosslinking polymer emulsion is Air Products
AIRFLEX−120 (T ₃₀₀ −20℃) from Company
It is available under the trade name. The catalyst is usually included with the self-crosslinking polymer according to the manufacturer's instructions. Preferably about 0.2% to 0.4% ammonium chloride (based on the total weight of the adhesive formulation) is added as a catalyst for the self-crosslinking emulsion polymer. Gluing a mixture of PVA (component 1), a water-based emulsion of a self-crosslinking polymer (component 2) and a water-based emulsion of a non-self-crosslinking polymer (component 3) The agent composition is applied to the web. After the adhesive composition is applied to the web, the adhesive is typically cured by heating the web. The polymer emulsion drives off the accompanying water and cures the polymer to increase its effectiveness as a textile adhesive at about 135°C (approx.
Temperatures of 275°C to about 177°C (about 350°C) are preferred. Lotion Agent The bonded and cured web is wetted (usually saturated) with a lotion agent. The lotion is an aqueous solution containing borate ions (usually obtained from boric acid, although other equivalent sources of borate ions such as sodium borate can be used). The lotion must contain an effective amount of borate ions sufficient to form a gel with the polyvinyl alcohol and provide wet strength to the web. This effective amount is usually present in a solution of at least 0.5% boric acid at a pH in the range of about 8.0 to 10.0. Lotions containing 0.5% to 1.5% boric acid are preferred. The pH of the water lotion is preferably adjusted to the alkaline side. A pH in the range of 8 to 9 is particularly suitable when buffered with a suitable buffer such as triethanolamine. Preferably the web is about 100% to about 600% based on the air dry weight of the web.
wet-packed with a lotion agent to obtain a suitable pre-humidified wiper with high wet strength. The PVA component of the adhesive composition interacts with the borate ions in the lotion to produce a water-resistant gel that strengthens the web while wetted with the borate-containing lotion. This interaction is due to the α-
hydroxy aliphatic acids, o-aromatic hydroxy acids,
It is synergistically enhanced with ions of cycloaliphatic alpha hydroxy acids or keto acids. Said compounds capable of forming complexes with borate ions in water-based lotions significantly increase the effectiveness of the lotion. The complex is
form a gel with PVA to strengthen the web, and
PVA gel keeps it dispersible. The above acids and salts of these acids, such as the sodium, potassium, lithium, ammonium and magnesium salts, which are capable of forming complexes with borate ions are suitable. The ability of the organic acid or its salt to form a complex with borate ions is indicated by an increasing increase in the conductivity of the boric acid solution in the presence of the organic acid or its salt. "Increasing increase in conductivity" refers to the increase in the observed conductivity of the organic acid (or salt) and boric acid solution minus the sum of the individual conductivities of the organic acid (or salt) and boric acid solution. means.
Particularly suitable are the salts of α- or o-hydroxycarboxylic acids, especially α-hydroxy dibasic acids. Sodium tartrate, potassium tartrate, potassium citrate, and lactate and salicylate salts are highly suitable, with potassium citrate being most preferred.
suitable α-hydroxy acids, o-aromatic hydroxy acids capable of increasing the conductivity of boric acid solutions;
List of keto acids and alicyclic alpha-hydroxy acids
Organoboron Chemistry, Volume 1, Howard
Included in Table 16-2 beginning on page 748 of Steinberg, Interscience Publishers, 1964. The sodium, potassium, lithium, ammonium, and magnesium salts of these acids are particularly suitable for use with borate ions in the lotions of this invention. Part of Organoboron Chemistry text
Table 16-2 shows α-
Hydroxy acids, o-aromatic hydroxy acids with 7 to 11 carbon atoms, cycloaliphatic alpha-hydroxy acids with 4 to 8 carbon atoms, and ketonic acids with 3 to 10 carbon atoms. It shows that acids are suitable. The molar ratio of borate substance in solution: the above compound capable of forming a complex with borate is 0.1:1
Must be between 1.6:1 and preferably 0.5:1.
It is 1. For this ratio, the dissociated compounds (ions) in the lotion solution are considered to be equivalent to the undissociated compounds. The example below shows that the web retains substantial wet strength during prolonged contact with a water-based lotion, even under extreme conditions, but the web retains its strength when the web is exposed to large amounts of water. The functional effect of the present invention is shown in that an adhesive formulation is obtained that exhibits dispersibility when tested to substantially reduce wet strength. All percentages and parts given herein are by weight unless otherwise indicated. Example: Multiple samples of dry-formed air-laid webs having about 85% wood pulp fibers and about 15% synthetic fibers (rayon fibers) are cast onto a porous surface, and 12% adhesive is applied onto the webs. and subsequently this web by spraying on
It was cured by exposing it to a temperature of 325°C for about 4 minutes. The air-laid, bonded, cured web was then encapsulated in a package containing a water-based lotion that wetted the web with about 250% lotion based on the weight of the web. This sealed package is then heated to 23.9°C (75〓) or 63°C (145°C) before opening.
〓) for various times and the dispersibility of this web was tested. The dispersibility of this web is 8.5 inches (21.59 cm) in diameter and 9 3/4 inches (24.8 cm) in height.
(inch) in an apparatus comprising a cylindrical vessel with a hemispherical stirrer located a short distance above the bottom and centered on the axis in the vessel. To test the dispersibility of the web, a container was filled with 4 liters of water kept at a temperature between 15°C and 20°C and a stirrer was turned on.
It was rotated at 650 rpm to create a vortex in the water.
Web sample piece [12.7cm (5 inches) x 12.7cm
(5 inches)] was immersed in agitated water, keeping it outside of the centrally generated vortex. This sheet is approximately
The time required to disintegrate into approximately ¹ inch square pieces was observed and recorded as dispersion time in seconds. If this sheet is not dispersed within 2000 seconds, the test will be stopped after 2000 seconds. Such sheets are confirmed as non-dispersive and give a rating of 2000+ seconds. Using the procedure described above, 26 web samples were
Adhesion was made using an adhesive composition as shown in the table (ammonium chloride is a catalyst). After curing the adhesive, the web was wet packaged with a water-based lotion containing borate ions and/or other ingredients as shown in Table 1. This packaged, lotion agent impregnated wiper sample was then removed from the package, tested for tensile strength while wet with lotion agent, and tested for dispersion after each storage test. The effects of different storage of wipers at ambient temperature and high temperature were tested. Table 2, on the other hand, provides detailed wet strength and dispersibility results for web samples treated with the ingredients shown in Table 1. Table 2 shows the wet tensile strength (g/cm) and dispersibility (seconds) of web samples treated with the ingredients shown in Table 1. The dispersibility column in Table 2 headed "23.9°C (75〓)" indicates the dispersibility of the web after packaging with lotion and storage for various periods specified. In the column headed "63℃ (145〓)" for each of the dispersibility and wet strength, the packaged product should be kept at 63℃ (145〓) for the specified 5 or 7 days.
The test results of dispersibility and wet tensile strength after holding are shown. Similarly, the wet strength "23.9℃
The column headed ``(75〓)'' gives the wet tensile strength in ``g/cm (oz/in)'' of the web still wet with lotion after storage for the indicated period of time. (For example, 188.3 (16.9) is 188.3 g/cm (16.9 oz/in) while the web is still wet with lotion after the specified storage period (1 week).
). The abbreviations related to component 2 and component 3 used in the column of adhesive components in Table 1 have the following meanings: (1) HA-4: Product name "RHOPLEX HA-4"
A non-self-crosslinking, non-ionic acrylic polymer (T ₃₀₀ =-17°C) available from Rohm and Haas Company. (2) B-15: Non-self-crosslinking acrylic polymer (T ₃₀₀ =
-4℃). (3) EI: Du as product name "ELVACE 1961"
Non-self-crosslinking ethylene-vinyl acetate based copolymer (T ₃₀₀ = +25°C) available from Pont. (4) HA-8: Product name “RHOPLEX HA-8”
A self-crosslinking acrylic polymer (T ₃₀₀ ) available from Rhom and Haas Company as
= -14℃). (5) A-120: As the product name "AIRFLEX-120"
Self-crosslinking ethylene-vinyl acetate based copolymer (T ₃₀₀ =-20°C) available from Air Products Company. (6) TR−520: Product name “RHOPLEX TR−520”
T ₃₀₀ is a self-crosslinking acrylic polymer available from Rohm and Haas Company as
= -8°C). Significance Table 2 shows that the combination of the three key components in the adhesive formulation combined with the presence of alpha-hydroxy acid (citrate) and borate ions in the lotion formulation It has been shown that this case is effective in adhering nonwoven fibrous webs of wood pulp fibers (sample numbers 1 to 7 and 9). Webs treated with such five components retain their dual functional effect of providing wet tensile strength even after long-term exposure to water lotions even after high temperature storage, while maintaining the activated amount of borate ions. The web can be dispersed without losing its wet strength when exposed to large amounts of water. When α-hydroxy acid is missing from the above components (outside the present invention), the water dispersibility becomes poor (Sample No. 8).
Polyvinyl alcohol and borate systems (outside the present invention) by themselves do not maintain this dispersibility and wet strength over the typical exposure times of webs in water lotions and the storage conditions encountered during shipping of these products. Similarly, combining a self-crosslinking latex with a non-self-crosslinking latex lacking either polyvinyl alcohol or α-hydroxy acid (outside the present invention) Cannot possess dual functional effects (sample numbers 10-12 and A-O).

【table】

[Table] * Borax instead of boric acid as a boric acid ion source ** Potassium tartrate instead of potassium citrate,
sodium

【table】

[Table] * 7 days instead of 5 days

Claims (1)

Claims: 1. A nonwoven adhesive bonded web moistened with a lotion agent, the wet web comprising at least
an adhesive composition having a tensile strength of 4.0 oz/in (44.56 g/cm), wherein the adhesive bond obtains at least a portion of its adhesive properties through interaction with borate ions in the lotion agent; The adhesive composition comprises (A) about 5 to about 15 parts of cold water soluble polyvinyl alcohol having a degree of hydrolysis of about 70% to about 90% and a degree of polymerization of at least 450;
(B) has a molecular weight of at least 100,000 and has a glass transition temperature of from about -50°C to about +45°C having a torsion modulus of 300 Kg/cm ² capable of acting as a fiber adhesive; non-self-crosslinking water-dispersible polymer from about 1.5 to about
2.5 parts and (c) capable of acting as a fiber adhesive;
the molecular weight is at least 100,000 and the air-dried film of the polymeric solid has a torsional modulus of 300 Kg/cm ² and a glass transition temperature of from about -50°C to about +
A water-dispersible, self-crosslinking polymer that is approx. 45℃
The lotion agent is an aqueous solution containing the polyvinyl alcohol component of the adhesive and an effective amount of borate ions to form a gel, and contains 0.75 to about 1.25 parts of the three components. Further, α-hydroxy aliphatic acids, o-aromatic hydroxy acids, cycloaliphatic α-hydroxy acids, keto acids or salts thereof, which can be formed.
containing a boric acid material to 1.6:1 molar ratio of the complexing acid or salt, and the web is wetted with an amount of the lotion agent equal to at least 100% of the weight of the web. A nonwoven adhesive bonded web moistened with a lotion agent, characterized in that: 2. The web is a dry-formed web, and the non-self-crosslinking polymer is a polyacrylic ester having a glass transition temperature in the range of -46°C to +30°C for air-dried films of polymeric solids; 2. The nonwoven web of claim 1, wherein the polyacrylic acid ester has a glass transition temperature of -22°C to +33°C for an air-dried film of the polymeric solid. 3. The nonwoven web of claim 1, wherein the lotion contains about 0.5% to about 1.5% boric acid and is buffered to have a PH in the range of about 8 to 10. 4 This combination is approximately 100% based on the air-dry weight of the web.
The nonwoven web of claim 1, wherein the nonwoven web is present in a package containing the web moistened with % to about 600% of a lotion agent. 5. The nonwoven web according to claim 1, wherein the α-hydroxy acid or its salt is citric acid or potassium citrate.