Patent Description:
Conventionally, there has been known dry sheets for cleaning each formed as a fiber sheet formed by interlacing a resin net and fiber. Some of such dry sheets for cleaning have a front surface or a back surface which has been patterned in a bump and dent shape (for example, see Patent Document <NUM>). Patent Document <NUM> discloses a dry sheet for cleaning comprising multiple layers, comprising: fiber layers each arranged in a front surface layer and a back surface layer; a nonwoven fabric layer provided in an intermediate layer between the fiber layers; and an interlaced part in which the fiber layers are interlaced with the nonwoven fabric layer, wherein the interlaced part is provided in the front surface layer and the back surface layer and includes slightly interlaced parts and highly interlaced parts, each of the highly interlaced parts being formed in a dent shape and being interlaced so as to have a higher fiber density than each of the slightly interlaced parts, wherein the highly interlaced parts in the front surface layer are formed corresponding to and at almost same spots as the highly interlaced parts in the back surface layer, wherein the highly interlaced parts are formed in an area ratio of <NUM> to <NUM>% with respect to an area of the front surface layer and the back surface layer in a plan view. Furthermore, Patent Document <NUM> discloses that the two outer layers are each individually produced using water-jet bonding. The laminate consisting of three layers is produced by means of thermal bonding. Patent Document <NUM> also discloses as already explained in connection with patent document <NUM> a dry sheet for cleaning comprising multiple layers, namely two fiber sheet layers and one core layer. It is also described that each of the fiber sheets disclosed is water-jet bonded. The fiber sheets and the core layer are heat-bonded with an adhesive or sewn at bonding portions.

However, in forming the bump and dent shape of the respective dry sheets for cleaning described in Patent Document <NUM>, the fiber of the entire sheet is interlaced in a state where the dry sheet is along the bump and dent shape. That is, in the bump and dent shape, the bump parts and the dent parts are formed on the respective front side and back side and combined with each other. Accordingly, the bump parts are also affected by the interlacing of the fiber. As a result, the density of the fiber forming the bumps and dents is substantially uniform in the entire sheet. In other words, the collection efficiency and collection characteristics of the entire sheet are substantially uniform, and there is a problem that the collection efficiency varies depending on the weight and size of the objects to be collected such as trash and dust.

An object of the present invention is to provide a dry sheet for cleaning which exhibit excellent collection efficiency regardless of the weight and shape of the objects to be collected.

In order to achieve the object, according to the invention according to claim <NUM>, there is provided a dry sheet for cleaning includes:.

According to the invention of claim <NUM>, the dry sheet for cleaning has the highly interlaced parts in which fiber is interlaced in a density higher than in the slightly interlaced parts in the interlaced part in the front surface layer and the back surface layer. By constituting the fiber in the front surface layer and the back surface layer as described above, the dry sheet for cleaning has spots having different fiber densities in each of the front surface layer and the back surface layer.

Therefore, the dry sheet for cleaning exhibits different collection efficiencies and collection characteristics on the spots having different fiber densities, that is, at the highly interlaced parts and the slightly interlaced parts, so as to suitably collect the objects to be collected having different weights and sizes at the respective spots.

Therefore, the dry sheet for cleaning can be bulky and exhibit improved collection efficiency.

Furthermore, the highly interlaced parts in the front surface layer are formed corresponding to and at almost same spots as the highly interlaced parts in the back surface layer. When the highly interlaced parts are formed at different spots, it is not possible to obtain the assumed bulkiness, for example, since the water-jet interlacing is intended to be done only on one side, but is also done on the opposite side in practice. However, there is no such disadvantage according to the present invention. That is, since the spots hit by the water flow are to be the highly interlaced parts in both layers, unnecessary interlacing is not done at the slightly interlaced parts.

Furthermore, as the fiber diameter of the polyethylene terephthalate fiber constituting the hydrophobic fiber is <NUM> dtex or more, the rigidity (cushioning property) of the fiber improves, making it possible to handle the dry sheet with a little force. Moreover, polyethylene terephthalate fiber with a large fiber diameter of <NUM> dtex or more contributes to keeping inter-fiber voids so that the objects to be collected are suitably collected.

As the highly interlaced parts are formed in an area ratio of <NUM> to <NUM>% to an area of the front surface layer and the back surface layer in a plan view, it is possible to suitably set the distribution and rate of the parts having different fiber densities.

As the highly interlaced parts and the slightly interlaced parts extend in a direction almost perpendicular to a wiping direction of the dry sheet for cleaning and are formed alternately and successively in the wiping direction, the dry sheet for cleaning can collect trash and/or dust at the parts with high fiber density and the parts with low fiber density alternately. Since various kinds of dust and dirt can be collected at each of the highly interlaced parts and the slightly interlaced parts, the dry sheet exhibits good collection efficiency.

The dry sheet for cleaning according to the present invention exhibits excellent collection efficiency regardless of the weight and shape of the objects to be collected.

Hereinafter, the dry sheet for cleaning as an embodiment of the present invention is described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

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

As shown in <FIG>, the dry sheet for cleaning <NUM> is provided with an inner layer <NUM> as a nonwoven fabric layer and outer layers <NUM> as fiber layers.

The inner layer <NUM> is an intermediate layer arranged between the outer layers <NUM> described later and formed of a nonwoven fabric. The inner layer <NUM> is preferably a spun bond nonwoven fabric from the viewpoint of durability. The durability is preferably <NUM> (N/<NUM>) or more in a wiping direction (CD direction) on the surface for cleaning and <NUM> (N/<NUM>) or more in a direction (MD direction) perpendicular to the CD direction. The grammage of the inner layer <NUM> is preferably set to be in the range of <NUM> to <NUM>/m<NUM>.

Natural fiber such as pulp, cotton, and hemp and cellulosic chemical fiber such as rayon and acetate may be used for the inner layer <NUM>.

Here, in the dry sheet for cleaning, the wiping direction of the surface for cleaning is a direction perpendicular to the longitude direction of a predetermined tool to which the dry sheet for cleaning is attached. That is, it is a direction along the moving direction during cleaning.

As shown in <FIG>, the outer layers <NUM> form a front surface layer and a back surface layer of the dry sheet for cleaning <NUM> and are each mainly formed of hydrophobic fiber. Specifically, the weight ratio of the contained hydrophobic fiber to the total weight of the outer layers <NUM> is <NUM> to <NUM>%.

Water is poured with a small water pressure of less than <NUM> kPa to the whole area of the outer layers <NUM> in pre-interlacing to combine the inner layer <NUM> and the outer layers <NUM>, and after that, the first water-jet interlacing is done with a water pressure of <NUM> to <NUM> kPa. After that, the bump and dent shape is formed by second water-jet interlacing with a water pressure of <NUM> to <NUM> kPa for spot (s) to be patterned part (s) <NUM> described later.

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 patterned part <NUM> is formed such that the pattern of bump and dent shape on the front surface layer corresponds to that on the back surface layer at the same spots.

Chemical fiber mainly composed of polyethylene terephthalate, polypropylene, polyethylene, etc. are used as the outer layers <NUM>.

The polyethylene terephthalate fiber is preferably included at a rate of <NUM>% or more, and the fiber diameter is preferably <NUM> dtex or more.

With the fiber diameter of <NUM> dtex or more, the fiber has improved rigidity (cushioning property), and it is possible to handle the dry sheet with a little force. Moreover, polyethylene terephthalate fiber with a large fiber diameter of <NUM> dtex or more may contribute to keep inter-fiber voids so that the objects to be collected such as trash and dust are suitably collected.

As shown in <FIG>, the outer layers <NUM> each include the patterned part(s) <NUM> as highly interlaced part(s) and non-patterned part(s) <NUM> as slightly interlaced part(s).

The second water-jet interlacing is done on the outer layers <NUM> which have been combined by the first water-jet interlacing. The fiber after the second water-jet interlacing is entangled more than that only after the first water-jet interlacing such that the patterned part <NUM> is formed. Therefore, the fiber density of the patterned part <NUM> is higher than that of the non-patterned part <NUM>. As a result, the patterned part <NUM> has a concaved shape deeper than the non-patterned part <NUM>. That is, the patterned part <NUM> has 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>.

Further, in the second water-jet interlacing, the water-jet interlacing of the outer layers <NUM> (the front surface layer and the back surface layer) is done at the corresponding parts (at the same spots) from both surfaces. That is, the patterned parts <NUM> are formed at the corresponding parts (at the same spots) on the outer layers <NUM> (on the front surface layer and on the back surface layer). In other words, when water-jet interlacing is done only on the front surface layer or the back surface layer, the bulky fiber of the opposite surface layer may be also crushed and diminished in size even without water-jet being interlaced. However, there is no such disadvantage according to the present invention. Therefore, the high bulkiness of the dry sheet for cleaning <NUM> can be maintained.

The patterned parts <NUM> are extended along the direction (MD direction) perpendicular to the wiping direction (CD direction) when the dry sheet for cleaning <NUM> is used. The patterned parts <NUM> are formed in multiple rows separated from each other at predetermined intervals. An area ratio of these patterned parts <NUM> are <NUM> to <NUM>% with respect to the surface area, in a plan view of the front surface or the back surface of the dry sheet for cleaning <NUM>. Specifically, the area ratio is calculated using a unit length determined to be the width of one of the patterned parts <NUM> and a unit length determined to be the width of one of the non-patterned parts <NUM> in the CD direction. For example, if the width of the patterned part <NUM> is <NUM> and the width of the non-patterned part <NUM> is <NUM>, the area ratio is <NUM>%. Here, the area ratio represents a ratio between the patterned surface A and the non-patterned surface B, where the patterned surface A is a surface area in a plan view of the patterned parts <NUM> and the non-patterned surface B is a surface area in a plan view of the non-patterned parts <NUM>. The area ratio is calculated by the following formula.

Preferably, the outer layers <NUM> each have a grammage of <NUM> to <NUM>/m<NUM> and include two or more kinds of chemical fiber (synthetic fiber) in combination.

Since the non-patterned parts <NUM> are not subjected to the second water-jet interlacing, they are not affected by compression other than the fiber compression resulting from the pre-interlacing or the first water-jet interlacing, and have fiber density less than that of the pattered parts <NUM>. In other words, in the non-patterned parts, fiber is easy to move freely. These non-patterned parts <NUM> mainly slide on the surface to be cleaned during wiping operation with the dry sheet for cleaning <NUM>. That is, they may greatly contribute to the collection property of the dry sheet <NUM> for cleaning.

As described above, the dry sheet for cleaning <NUM> has the outer layers <NUM> as collection surfaces in which the patterned parts <NUM> with high fiber density and the non-patterned parts <NUM> with low fiber density are alternately arranged. In addition, the parts with high fiber density have high collection efficiency for heavy trash, and the parts with low fiber density have high collection efficiency for light trash.

Therefore, it is possible to collect both heavy trash and light trash with one dry sheet for cleaning <NUM>. Furthermore, since the ratio between the patterned parts <NUM> and the non-patterned parts <NUM> is in the range of <NUM>-<NUM>% according to the present invention, it is possible to preferably balance the collection efficiency of heavy trash with that of light trash.

According to the present embodiment, the dry sheet for cleaning <NUM> is provided with the patterned parts <NUM> having higher fiber density than the other parts in the front surface layer and the back surface layer. That is, the front surface layer or the back surface layer of the dry sheet for cleaning <NUM> have parts having different fiber densities.

Therefore, it is possible to suitably collect the objects to be collected having various weights and sizes at the respective parts having different fiber densities due to different collection efficiencies and collection characteristics.

Furthermore, the patterned parts <NUM> in the front surface layer are formed corresponding to and at almost same spots as the patterned parts <NUM> in the back surface layer. When the patterned parts <NUM> are formed at different spots, it is not possible to obtain the assumed bulkiness, for example, since the water-jet interlacing is intended to be done only on one side, but is also done on the opposite side in practice. However, there is no such disadvantage according to the present invention. That is, since the spots hit by the water flow are to be the patterned parts <NUM> on both surfaces, unnecessary interlacing is not done at the non-patterned parts <NUM>.

Accordingly, the dry sheet for cleaning <NUM> can be bulky and exhibit improved collection efficiency.

According to the present embodiment, since the area ratio of the patterned parts <NUM> are <NUM> to <NUM>% with respect to the front or back surface in a plan view, it is possible to suitably set the distribution and rate of the spots having different fiber densities and to achieve excellent collection efficiency for various kinds of trash.

According to the present embodiment, since the patterned parts <NUM> are extended along the direction perpendicular to the wiping direction, the dry sheet for cleaning <NUM> can collect trash and/or dust at the patterned parts <NUM> and the non-patterned parts <NUM> alternately. Since various kinds of dust and dirt can be collected at each of the patterned parts <NUM> and the non-patterned parts <NUM>, the dry sheet exhibits good collection efficiency.

According to the present embodiment, since a spun bond nonwoven fabric is used as the inner layer <NUM>, there is no disadvantage of damaging the surface to be cleaned by a resin net, which has been used conventionally.

According to the present embodiment, the patterned parts <NUM> and the non-patterned parts <NUM> are both formed by water-jet interlacing, specifically, respectively formed by pre-interlacing and by further interlacing for patterning. Thus, it is possible to manufacture the dry sheet for cleaning <NUM> easily.

In a case where the patterned parts <NUM> are formed by a heat roll or the like, for example, the non-patterned parts <NUM> are also pressed by the roll such that the fiber at the non-patterned parts <NUM> is also crushed. This results in smaller difference in fiber density and a reduced variety in collection efficiency. However, since only the patterned parts <NUM> are pressed by water with high pressure in the interlacing for patterning, there is no such disadvantage according to the present embodiment.

The present invention is not limited to the embodiment described above and modification examples, and it is natural that the specific configurations may be suitably modified.

In the dry sheet for cleaning <NUM> of Example <NUM>, the outer layers <NUM> were fibrous webs including polyethylene terephthalate as a main component and the inner layer <NUM> was a spun bond nonwoven fabric.

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

Specifically, the outer layers <NUM> were each composed of hydrophobic fiber by <NUM>%, where polyethylene terephthalate was contained by <NUM>% as the 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.

The width of the respective patterned parts <NUM> formed on the outer layers <NUM> was <NUM> in the CD direction, and the width of the respective non-patterned parts <NUM> was <NUM> in the CD direction. That is, the area ratio of the patterned parts <NUM> to the surface area of the outer layers <NUM> in a plan view was <NUM>%.

Further, in the dry sheet for cleaning <NUM> of Example <NUM>, the width of the respective patterned parts <NUM> formed on the outer layers <NUM> was <NUM> in the CD direction, and the width of the respective non-patterned parts <NUM> was <NUM> in the CD direction. That is, the area ratio of the patterned parts <NUM> to the surface area of the outer layers <NUM> in a plan view was <NUM>%.

In the dry sheet for cleaning <NUM> of Example <NUM>, the width of the respective patterned parts <NUM> formed on the outer layers <NUM> was <NUM> in the CD direction, and the width of the respective non-patterned parts <NUM> was <NUM> in the CD direction. That is, the area ratio of the patterned parts <NUM> to the surface area of the outer layers <NUM> in a plan view was <NUM>%.

In the dry sheet for cleaning <NUM> of Comparative Example <NUM>, the width of the respective patterned parts <NUM> formed on the outer layers <NUM> was <NUM> in the CD direction, and the width of the respective non-patterned parts <NUM> was <NUM> in the CD direction. That is, the area ratio of the patterned parts <NUM> (strictly speaking, not the patterned parts <NUM> but a processed part where interlacing for patterning has been done in this Example) to the surface area of the outer layers <NUM> in a plan view was <NUM>%.

In the dry sheet for cleaning <NUM> of Comparative Example <NUM>, the width of the respective patterned parts <NUM> formed on the outer layers <NUM> was <NUM> in the CD direction, and the width of the respective non-patterned parts <NUM> was <NUM> in the CD direction. That is, the area ratio of the patterned parts <NUM> to the surface area of the outer layers <NUM> in a plan view was <NUM>%.

In the dry sheet for cleaning <NUM> of the Comparative Example <NUM>, the width of the patterned parts <NUM> formed on the outer layers <NUM> was <NUM> in the CD direction, and the width of the non-patterned parts <NUM> was <NUM> in the CD direction. That is, the area ratio of the patterned parts <NUM> to the surface area of the outer layers <NUM> in a plan view was <NUM>%.

The dry sheet for cleaning <NUM> of Comparative Example <NUM> had the outer layers <NUM> including fibers of the same kinds as but at different blend ratio from the fibers in the Examples, and evaluated.

That is, the outer layers <NUM> included PET of <NUM> dtex by <NUM>% and binder fiber by <NUM>%. the width of the respective patterned parts was <NUM> and the width of the respective non-patterned parts was <NUM> (patterning rate <NUM>%), as well as in Example <NUM>.

The test of floor wiping was executed using the dry sheets for cleaning <NUM> in Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM> described above.

The test method involved attaching the dry sheet for cleaning <NUM> to a fixing tool of the dry sheet for cleaning <NUM> not described in the drawings and wiping the floor surface formed of an acryl board by sliding on it.

As for the fixing tool, a flat board member was attached to the tip of a stick member (grip), rotatable in all the directions. The dry sheet for cleaning <NUM> was attached to the flat board member.

A weight of <NUM> was attached to the flat board member so that the pushing pressure between the dry sheet for cleaning <NUM> and the floor surface was constant.

As the test of the collection efficiency, some kinds of objects to be collected were placed on the surface to be wiped which was the floor surface made of an acryl board, and the amount of collected objects was measured.

In a wiping action, the dry sheet for cleaning <NUM> was moved by <NUM> from the center to the right, by <NUM> to the left, and by <NUM> to the right again, on the surface to be wiped of <NUM> in width to go and back a single time on the surface to be cleaned.

The test was executed for three kinds of objects to be collected, dust, sesame seed for heavy trash, and hair for light trash.

Specifically, hairs H were wiped as <NUM> hairs H were placed along the wiping direction and <NUM> hairs H were placed perpendicular to the wiping direction, as shown in <FIG>. Sesame seeds were arranged in three rows which each include three, four, and three seeds in this order placed perpendicular to the wiping direction.

As for dust, JIS Z <NUM> test powders <NUM> No. <NUM> (Kanto loam layer) which passed through a sieve of <NUM> mesh were obtained by <NUM> and placed in a bordered area of <NUM> × <NUM> of the floor surface. Then, the amount of dust wiped off was checked visually and evaluation was made from A (dust was caught) to C (dust was not caught) was made.

The results of test and evaluation are shown in Table <NUM>.

As shown in Table <NUM>, in the results of Examples <NUM> to <NUM>, four or five out of ten sesame seeds S for heavy trash could be collected and four or five out of five hairs H for light trash could be collected (except in Example <NUM>). It could be observed that dust was collected well in any of the Examples. That is, it could be observed that Examples <NUM> to <NUM> exhibit good collection property and that Examples <NUM> to <NUM> in particular exhibit even more excellent collection property.

According to Comparative Example <NUM> where a patterning rate was <NUM>%, collection efficiency of equal to or more than those according to Examples <NUM> to <NUM> could be exhibited as for sesame seeds S, for which five or six out of ten could be collected, however, collection efficiency could be hardly exhibited as for hairs H, for which zero or one out of five was collected.

According to Comparative Examples <NUM> and <NUM> where a patterning rate was <NUM>%, collection efficiency could be hardly exhibited as for sesame seeds S, for which one out of ten was collected, however, good collection efficiency could be exhibited as for hairs H, for which five out of five was collected. Further, collection efficiency of dust was low according to Comparative Example <NUM>, but it was good according to Comparative Example <NUM>.

According to Comparative Example <NUM> where the blending ratio of PET fiber (<NUM> dtex) is smaller than Examples by <NUM>% and the patterning rate was <NUM>%, collection efficiency could be hardly exhibited as for sesame seeds S, for which one out of ten was collected, or as for hairs H, for which one out of five was collected. Further, according to Comparative Example <NUM>, collection efficiency for dust was also poor.

From the above, it was found that, if the patterning rate is <NUM>% or more, good collection efficiency is exhibited as for heavy trash, but collection efficiency cannot be exhibited as for light trash.

Further, it was found that, if the patterning rate is <NUM>% or less, good collection efficiency is exhibited as for light trash, but collection efficiency cannot be exhibited as for heavy trash.

Further, it was found that, if the patterning rate is within the range of <NUM>-<NUM>%, good collection efficiency is exhibited as for both heavy trash and light trash.

Claim 1:
A dry sheet (<NUM>) for cleaning comprising multiple layers (<NUM>; <NUM>), comprising:
fiber layers (<NUM>) each arranged in a front surface layer and a back surface layer;
a spun bond nonwoven fabric layer (<NUM>) provided in an intermediate layer between the fiber layers; and
an interlaced part in which the fiber layers are interlaced with the nonwoven fabric layer,
wherein the interlaced part is provided in the front surface layer and the back surface layer (<NUM>) and includes slightly interlaced parts (<NUM>) and highly interlaced parts (<NUM>), each of the highly interlaced parts (<NUM>) being formed in a dent shape and being interlaced so as to have a higher fiber density than each of the slightly interlaced parts (<NUM>),
wherein the highly interlaced parts (<NUM>) in the front surface layer are formed corresponding to and at almost same spots as the highly interlaced parts (<NUM>) in the back surface layer,
characterized in that the front surface layer and the back surface layer (<NUM>) each include polyethylene terephthalate fiber at a rate of <NUM>% or more,
wherein a fiber diameter of the polyethylene terephthalate fiber is <NUM> dtex or more,
wherein the highly interlaced parts (<NUM>) are formed in an area ratio of <NUM> to <NUM>% with respect to an area of the front surface layer and the back surface layer in a plan view, and
wherein the highly interlaced parts (<NUM>) and the slightly interlaced parts (<NUM>) each extend in a direction (MD) perpendicular to a wiping direction (CD) of the dry sheet (<NUM>) for cleaning and are formed alternately and successively in the wiping direction (CD).