Patent Description:
Conventionally, there have been known wet sheets for cleaning which are made of sheet material impregnated with chemical solution. Some of such wet sheets are formed with multiple layers, where hydrophilic fiber such as rayon is provided as an inner layer and hydrophobic fiber such as polypropylene is provided as an outer layer, and the hydrophilic fiber of the inner layer is impregnated with chemical solution (ex. Patent Document <NUM>).

Moreover, <CIT> reveals a wet sheet according to the preamble of claim <NUM>.

However, the wet sheet for cleaning described in Patent Document <NUM> is wet on the surface, which increases the frictional resistance with the floor surface in the cleaning of the floor and requires a high load for the wet sheet to slide on the floor surface, for example. The load is placed onto the wet sheet for cleaning, and the chemical solution with which the sheet is impregnated is excessively discharged. Then the wet sheet for cleaning is short of the chemical solution sooner. Thus, problematically, the surface to be cleaned may not be cleaned sufficiently.

The impregnation rate of the chemical solution or the grammage of the wet sheet for cleaning may be increased as a countermeasure to avoid the shortage of the chemical solution. However, it may increase the cost of producing the wet sheet for cleaning and decrease the price competitiveness as daily goods.

An object of the present invention is to provide a wet sheet for cleaning at a low price which may be used to wipe a larger area while discharging chemical solution by restraint of excessive discharge of the chemical solution and a method for producing the wet sheet for cleaning.

In order to solve the above problems, a wet sheet according the present invention is defined in claim <NUM>.

According to the invention of claim <NUM>, as the inner layer contains pulp by equal to or more than <NUM> wt%, has a grammage of <NUM> to <NUM>/m<NUM>, and occupies <NUM> to <NUM>% of the total mass of the wet sheet for cleaning, the chemical solution with which the sheet is impregnated is not excessively discharged and the wet sheet for cleaning may not be short of the chemical solution soon. As a result, the surface to be cleaned may be cleaned sufficiently. Moreover, as the hydrophobic fiber inner layer is adjacent to either of the hydrophobic fiber layers, the chemical solution with which the hydrophilic fiber inner layer is impregnated is not easily discharged to the side of the hydrophobic fiber layer adjacent to the hydrophobic fiber inner layer.

Thus, a larger area may be wiped while the chemical solution is being discharged.

The inner layer is mainly composed of pulp, which is cheaper than rayon. As pulp is used, the cost of the wet sheet for cleaning may be decreased and the price competitiveness as daily goods may be maintained or improved.

The present invention described in claim <NUM> is the wet sheet for cleaning according to claim <NUM>, wherein the hydrophobic fiber of the outer layers includes polyethylene terephthalate fiber at a rate of <NUM>% or more and a fiber diameter of the polyethylene terephthalate fiber is <NUM> dtex or more.

According to the invention of claim <NUM>, the effects equal to the invention of claim <NUM> may be consistently achieved. Moreover, the polyethylene terephthalate fiber of the outer layers with a fiber diameter equal to or more than <NUM> dtex improves the rigidity (cushioning property) of the fiber, making it possible to handle it with a little force. Moreover, the polyethylene terephthalate fiber with a large fiber diameter equal to or more than <NUM> dtex may keep inter-fiber voids not to cause capillary actions easily and prevent the chemical solution to be discharged from the inner layer to the outer layers.

The present invention described in claim <NUM> is the wet sheet for cleaning according to claim <NUM> or <NUM>, including an interlaced part where the outer layers and the inner layer are interlaced.

According to the invention of claim <NUM>, the effects equal to the invention of claim <NUM> or <NUM> may be consistently achieved. Moreover, with the interlaced parts where the outer layers and the inner layer are interlaced, the chemical solution may be restrained more certainly from being excessively discharged.

The present invention described in claim <NUM> is a method for producing the wet sheet for cleaning according to claim <NUM>, wherein the interlaced part is formed by water-jet interlacing.

According to the invention of claim <NUM>, the effects equal to the invention of claim <NUM> may be consistently achieved. Moreover, as the interlaced part is interlaced by the water-jet interlacing which allows interlacing of the inner layer and the outer layers to be interlaced without adhesion agent, a simple configuration is possible and the surface from which the chemical solution is discharged is not blocked by adhesion agent, which may prevent the unevenness of wiping.

The present invention may achieve a low price and increase an area to be wiped while chemical solution is being discharged by restraint of excessive discharge of the chemical solution.

Hereinafter, the wet sheet for cleaning as an embodiment of the present invention is described in detail with reference to the drawings.

The wet sheet for cleaning in the embodiment of the present invention is described on the basis of <FIG>.

The wet sheet for cleaning <NUM> is provided with an inner layer <NUM> and outer layers <NUM> which are hydrophobic fiber layers as shown in <FIG>.

The inner layer <NUM> is an intermediate layer which is arranged between the outer layers <NUM> described later. The basic structure of the inner layer <NUM> is a structure with a hydrophilic fiber inner layer <NUM> and a hydrophobic fiber inner layer <NUM>, which may be a two-layer structure, a multiple-layer structure with hydrophilic fiber inner layers <NUM> and hydrophobic fiber inner layers <NUM> being layered, or a mixed cotton of hydrophilic fiber and hydrophobic fiber.

The inner layer <NUM> is formed to have a grammage of equal to or more than <NUM>/m<NUM>, and a mass ratio of <NUM> to <NUM>% to the whole mass of the wet sheet for cleaning <NUM>.

The hydrophilic fiber inner layer <NUM> is a layer with hydrophilic fiber, and is arranged adjacent to an outer layer <NUM> which is the front surface layer of the outer layers <NUM> described later (the front surface layer here refers to the surface mainly sliding on the surface to be cleaned compared to the back surface layer).

According to the present invention, the hydrophilic fiber inner layer <NUM> is impregnated with the chemical solution described later. Pulp is mainly used as the hydrophilic fiber, and pulp is used in an amount equal to or more than <NUM> wt% to the total mass of the inner layer <NUM>.

Natural fiber such as cotton and hemp and cellulosic chemical fiber such as acetate may be used with pulp as the hydrophilic fiber. However, according to the present invention rayon is not included in the hydrophilic fiber.

The inner layer <NUM> contains pulp by equal to or more than <NUM> wt%, has a grammage of <NUM> to <NUM>/m<NUM>, and occupies <NUM> to <NUM>% of the total mass of the wet sheet for cleaning because the chemical solution is not certainly retained in the inner layer <NUM> if the conditions are below those and because the amount of the chemical solution and the weight of the sheet are larger to cause the sense of wiping and handling to be heavier if the conditions are above those.

The hydrophobic fiber inner layer <NUM> is a layer with hydrophobic fiber and is arranged adjacent to an outer layer <NUM> which is the back surface layer. Resin fiber such as polyethylene terephthalate, polypropylene, and polyethylene is used as the hydrophobic fiber.

Under some conditions of the sort of pulp or its contained amount, etc., pulp may not be sufficiently durable as the hydrophilic fiber inner layer <NUM> or may be unpreferable in terms of the size stability. In such a case, the durability of the sheet or the stability of the size may be kept by the hydrophobic fiber inner layer <NUM>.

The chemical solution is used as cleaning detergent of the wet sheet for cleaning <NUM> and is to be discharged from the front surface layer or the back surface layer through the outer layers <NUM> described later. The chemical solution is prepared with a viscosity of <NUM> to <NUM> mPa·s at <NUM>. The viscosity is measured using the Brookfield (B-type) rotational viscometer (model number: LVDV-I+) and the rotor to be used and the rotational frequency are suitably changed depending on the viscosity of the liquid detergent. The measurement is performed in conformity with JIS K <NUM>-<NUM>:<NUM> under the condition that the temperature is <NUM> and the rotational frequency is <NUM> rpm.

A lower alcohol such as ethanol, a surfactant such as benzalkonium chloride, a bactericide, and propylene glycol monomethyl ether (PGME) dissolved in water are used as the chemical solution, for example.

In this embodiment, the inner layer <NUM> has the hydrophobic fiber inner layer <NUM> adjacent to a side of the hydrophilic fiber inner layer <NUM>, though not limited thereto. For example, the hydrophilic fiber inner layer <NUM> adjacent to the hydrophobic fiber inner layers <NUM> on the both sides of the hydrophilic fiber inner layer <NUM> are put between the hydrophobic fiber inner layers <NUM>.

The outer layers <NUM> form the front surface layer and the back surface layer of the wet sheet for cleaning <NUM>, and each layer is formed with hydrophobic fiber. Chemical fiber mainly composed of polyethylene terephthalate, polypropylene, polyethylene, etc. are used as the hydrophobic fiber. The polyethylene terephthalate fiber is preferably included at a rate equal to or more than <NUM>%, and the fiber diameter is preferably equal to or more than <NUM> dtex.

With the fiber diameter equal to or more than <NUM> dtex, the rigidity (cushioning property) of the fiber improves, making it possible to handle it with a little force. Moreover, polyethylene terephthalate fiber with a large fiber diameter equal to or more than <NUM> dtex may keep inter-fiber voids not to cause capillary actions easily and prevent the chemical solution to be discharged from the inner layer <NUM> to the outer layers <NUM>.

The outer layer <NUM> includes an interlaced part <NUM> and a non-interlaced part <NUM>.

The interlaced part <NUM> is a part where the inner layer <NUM> and the outer layers <NUM> are combined by interlacing of the fibers of the layers. The water-jet interlacing is used as the method of interlacing of the interlaced part <NUM>. Specifically, water is poured to the whole area with a small water pressure of less than <NUM> kPa to combine the inner layer <NUM> and the outer layers <NUM> in pre-interlacing, and after that, the water-jet interlacing is done for a part to be the interlaced part <NUM> with a water pressure of <NUM> to <NUM> kPa. In such a way, the shape with a pattern of bumps and dents is formed.

Water hits the same spots on the front surface layer and the back surface layer from the both sides of the wet sheet for cleaning <NUM> in the water-jet interlacing. Accordingly, the interlaced part <NUM> is formed such that the pattern of bumps and dents on the front surface layer corresponds to that on the back surface layer at the same spots.

The fibers of the inner layer <NUM> and the outer layers <NUM> are entangled as a result of the water-jet interlacing and the fiber density is high at the interlaced part <NUM>. Thus, the fibers of the hydrophobic fiber forming the interlaced part <NUM> are not spatially free compared to the non-interlaced part <NUM> described later, and the fibers at the inter-laced part <NUM> do not move freely in a wiping action compared to those at the non-interlaced part <NUM>.

The interlaced part <NUM> is indented in a dent shape compared to the non-interlaced part <NUM> described later because of the high fiber density. That is, the interlaced part <NUM> includes a bottom <NUM> which is the bottom of the dent and an inclined part <NUM> which is an inclined surface connecting the non-interlaced part <NUM> described later and the bottom <NUM>.

The interlaced part <NUM> is extended along the direction (direction MD) perpendicular to the direction of wiping (direction CD) when the wet sheet for cleaning <NUM> is used. The interlaced parts <NUM> are formed in multiple rows separated at predetermined intervals. Those interlaced parts <NUM> are formed to have an area ratio of <NUM> to <NUM>% to the surface area of the front surface layer or the back surface layer of the wet sheet for cleaning <NUM> in a plan view. Here, the area ratio represents a ratio between the interlacing surface A and the non-interlacing surface B, where the interlacing surface A is a surface area of the interlaced parts <NUM> in a plan view and the non-interlaced surface B is a surface area of the non-interlaced parts <NUM> in a plan view. The area ratio is calculated by the following formula.

Nonwoven fabric mainly composed of polyethylene terephthalate, polypropylene, polyethylene, etc. is used as the hydrophobic fiber.

The non-interlaced part <NUM> is a part where only the pre-interlacing is done for the inner layer <NUM> and the outer layers <NUM>, but not the water-jet interlacing.

The non-interlaced part <NUM> is with a lower fiber density compared to the interlaced part <NUM> because the water-jet interlacing is not done, and the fibers at this part may move freely in the wiping action compared to the fibers at the interlaced part <NUM>.

The interlaced parts <NUM> and the non-interlaced parts <NUM> are arranged alternately along the wiping direction, and the surface to be cleaned first touches the non-interlaced part <NUM> only.

The pre-interlacing is not included in the water-jet interlacing process in the description. That is, defined as the water-jet interlacing is only the fiber interlacing process where water is poured with a high water pressure after the pre-interlacing. Thus, the non-interlaced part <NUM> for which the pre-interlacing only is done is, strictly speaking, slightly interlaced with the pre-interlacing but is treated as a part not interlaced, for convenience.

The static friction resistance value and the kinetic friction resistance value of the outer layer <NUM> are decreased in wiping of the surface to be cleaned compared to the case where the interlaced part <NUM> is not provided.

To sum up, as the friction resistance value is small when the surface to be cleaned is wiped with the wet sheet for cleaning <NUM>, a light touch of wiping may be obtained.

According to this embodiment, as the inner layer <NUM> contains pulp by equal to or more than <NUM> wt%, has a grammage of <NUM> to <NUM>/m<NUM>, and occupies <NUM> to <NUM>% of the total mass of the wet sheet for cleaning <NUM>, the chemical solution with which the sheet is impregnated is not excessively discharged and the wet sheet for cleaning <NUM> may not be short of the chemical solution soon. As a result, the surface to be cleaned may be cleaned sufficiently.

The inner layer <NUM> is mainly composed of pulp, which is cheaper than rayon. As pulp is used, the cost of the wet sheet for cleaning <NUM> may be decreased and the price competitiveness as daily goods may be maintained or improved.

As the hydrophobic fiber inner layer <NUM> is adjacent to the back surface layer of the outer layers <NUM>, the chemical solution with which the hydrophilic fiber inner layer <NUM> is impregnated is not easily discharged to the side of the outer layer <NUM> adjacent to the hydrophobic fiber inner layer <NUM>.

Thus, the chemical solution may be selectively discharged to the side of the front surface layer of the outer layers <NUM>, which may restrain discharge of the chemical solution not effective for cleaning.

According to this embodiment, as the wet sheet for cleaning <NUM> is provided with the interlaced parts <NUM> where the outer layers <NUM> and the inner layer <NUM> are interlaced, the chemical solution may be restrained more certainly from being excessively discharged.

According to this embodiment, as the front surface layer and the back surface layer are configured with hydrophobic fiber, the chemical solution with which the hydrophilic fiber inner layer <NUM> is impregnated may be suitably retained and discharged in an adjusted amount.

According to this embodiment, as the interlaced part <NUM> is interlaced by the water-jet interlacing which allows interlacing of the inner layer <NUM> and the outer layers <NUM> to be interlaced without adhesion agent, a simple configuration is possible and the surface from which the chemical solution is discharged is not blocked by adhesion agent, which may prevent the unevenness of wiping.

In Example <NUM>, the wet sheet for cleaning <NUM> as shown below was used.

Nonwoven fabric mainly composed of polyethylene terephthalate was used for the outer layers <NUM>.

Chemical fiber mainly composed of polyethylene terephthalate, polypropylene, polyethylene, etc. was used as the hydrophobic fiber.

Specifically, the outer layer <NUM> was composed of hydrophobic fiber by <NUM>%, where polyethylene terephthalate was contained by <NUM>% as hydrophobic fiber and core-sheath fiber of polypropylene and polyethylene was contained by <NUM>% as binder fiber. The polyethylene terephthalate fiber of <NUM> dtex in fineness and the binder fiber of <NUM> dtex in fineness were used.

As for the inner layer <NUM>, the hydrophilic fiber inner layer <NUM> was composed of pulp of <NUM>/m<NUM> in grammage, and the hydrophobic fiber inner layer <NUM> was composed of <NUM> dtex PP spunbond nonwoven fabric of <NUM>/m<NUM> in grammage. The inner layer <NUM> as a whole contained pulp by <NUM> wt% and hydrophobic fiber by <NUM> wt%.

Surfactants (anionic surfactant, nonionic surfactant, cationic surfactant and amphoteric surfactant) and water-soluble solvents (monohydric alcohol or polyhydric alcohol) in water as a solvent were used for the chemical solution. Used in this embodiment were Prestall by <NUM>% as nonionic surfactant, lauryldimethylamine oxide by <NUM>% as amphoteric surfactant, ethanol by <NUM>% and <NUM>-methoxy-<NUM>-propanol by <NUM>% as alcohol, and Benzalkonium chloride by <NUM>% as quaternary ammonium salt.

The grammage of the wet sheet for cleaning <NUM> was <NUM>/m<NUM>.

The ratio of the inner layer <NUM> to the wet sheet for cleaning <NUM> as a whole (inner layer/wet sheet for cleaning) was <NUM>%.

The area ratio of the interlaced part of the outer layer <NUM> was <NUM>%. The impregnation rate of the chemical solution was <NUM>%.

As for the inner layer <NUM>, the hydrophilic fiber inner layer <NUM> was composed of pulp of <NUM>/m<NUM> in grammage, and the hydrophobic layer inner layer <NUM> was composed of <NUM> dtex PP spunbond nonwoven fabric of <NUM>/m<NUM> in grammage. The inner layer <NUM> as a whole contained pulp by <NUM> wt% and hydrophobic fiber by <NUM> wt%.

The ratio of the inner layer <NUM> to the wet sheet for cleaning <NUM> (inner layer/wet sheet for cleaning) was <NUM>%.

The configurations besides the above were the same as those of Example <NUM>.

The area ratio of the interlaced part of the outer layer <NUM> was <NUM>%.

In Comparative Example <NUM>, the wet sheet for cleaning <NUM> as shown below was used.

The inner layer <NUM> was made of two hydrophilic fiber inner layers. The rayon layer had a grammage of <NUM>/m<NUM> and the pulp layer had a grammage of <NUM>/m<NUM>. The inner layer <NUM> as a whole contained rayon by <NUM> wt% and pulp by <NUM> wt%, being interlaced.

The inner layer <NUM> was made of pulp of <NUM>/m<NUM> in grammage. The inner layer <NUM> as a whole contained pulp by <NUM> wt%.

The test to count the number of times of wiping off was executed using the wet sheets for cleaning <NUM> in Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM> described above.

The method of the test to count the number of times of wiping off involved attaching the wet sheet for cleaning <NUM> to a tool for fixing the wet sheet for cleaning <NUM> (Quickle Wiper/year of production <NUM>, Kao Corporation) without slack and wiping the floor surface formed by an acryl board in one direction. An action of wiping off from edge to edge of the acryl board floor surface along the longitudinal direction of the acryl board floor surface (length <NUM>, width <NUM>) with the fixing tool of <NUM> in width was counted as one time.

The effective wiped area (m<NUM>) = <NUM>×<NUM>× (number of times).

The test described above was repeated <NUM> times and the measured value was to be the average value of the number of times of effective wiping action and the average value of the effective wiped area.

The test results to count the number of times of wiping off are shown in Table <NUM>.

The results shown in Table <NUM> are as follows.

In all of Examples <NUM> to <NUM>, the number of times of effective wiping action in which the chemical solution was recognized in the whole width of the wet sheet for cleaning <NUM> was equal to or more than <NUM> times. The effective wiped area was equal to or larger than <NUM><NUM> in all of Examples <NUM> to <NUM>.

Compared to those, in Comparative Examples <NUM> to <NUM>, the number of times of effective wiping action was equal to or less than <NUM> times, and the effective wiped area was equal to or smaller than <NUM><NUM>.

Claim 1:
A wet sheet for cleaning (<NUM>) comprising multiple layers and being impregnated with chemical solution, the wet sheet for cleaning (<NUM>) comprising:
outer layers (<NUM>) which are made of hydrophobic fiber and which are each arranged on a front surface and a back surface;
an inner layer (<NUM>) which has hydrophilic fiber and which is arranged between the outer layers (<NUM>),
wherein the inner layer (<NUM>) is provided with a hydrophilic fiber inner layer (<NUM>) with the hydrophilic fiber and a hydrophobic fiber inner layer (<NUM>) with hydrophobic fiber,
wherein the hydrophobic fiber inner layer (<NUM>) is adjacent to at least one of the outer layers (<NUM>), characterised in that the hydrophilic fiber inner layer (<NUM>) is impregnated with the with chemical solution and wherein rayon is not included in the hydrophilic fiber, and
the inner layer (<NUM>) includes pulp by <NUM> wt% or more, has a grammage of <NUM> to <NUM>/m<NUM>, and occupies <NUM> to <NUM>% of a total mass of the wet sheet for cleaning (<NUM>).