阅读说明：本技术 一种包芯防藻绳及其制作方法 (Core-spun algae-proof rope and manufacturing method thereof ) 是由 孙鹏程 宋炳涛 姜润喜 邱延平 杨斌 于 2020-12-10 设计创作，主要内容包括：本发明提出了一种包芯防藻绳,包括外皮层和内芯层,所述外皮层紧密包覆在内芯层外部,所述外皮层为编织结构或包塑结构,为编织结构的外皮层外涂覆防藻涂层,所述内芯层为合成纤维绳股的编织结构或捻制结构。本发明制作简便,性能优良,不仅可以提升绳索的破断强力和耐磨等性能,而且可以显著减少绿潮早期发生的初始生物附着量,进而达到防海藻目的。(The invention provides a core-spun anti-algae rope which comprises an outer skin layer and an inner core layer, wherein the outer skin layer is tightly coated outside the inner core layer, the outer skin layer is of a woven structure or a plastic-coated structure, an anti-algae coating is coated outside the outer skin layer of the woven structure, and the inner core layer is of a woven structure or a twisted structure of a synthetic fiber rope strand. The invention has simple and convenient manufacture and excellent performance, can not only improve the performances of breaking strength, wear resistance and the like of the rope, but also obviously reduce the initial biological attachment amount generated in the early stage of green tide, thereby achieving the aim of preventing algae.)

1. A core-spun algae-proof rope is characterized in that: including ectotheca and inner core layer, the inseparable cladding of ectotheca is outside at inner core layer, the structure is moulded for weaving structure or package to the ectotheca, for weaving the structure outer coating algae-proof coating of ectotheca, inner core layer is the weave structure or the system structure of twisting of synthetic fiber rope strand.

2. The cored algae-proof rope of claim 1, wherein: the braided structure of the outer skin layer is formed by braiding half of S-twist-direction and half of Z-twist-direction synthetic fiber strands.

3. The cored algae-proof rope of claim 1, wherein: the plastic-coated structure of the outer skin layer is formed by melting, extruding and coating plastic particles, and the thickness of the plastic-coated structure is 0.5-3 mm.

4. The cored algae-proof rope of claim 3, wherein: the plastic particles are one of PVC particles, TPE particles, ABS environment-friendly particles, TPU particles and TPR particles.

5. The cored algae-proof rope of claim 1, wherein: the algae-proof coating is a tough protective body formed by copolymerizing cetylpyridinium chloride amine modified chitosan, carbon hydroxyl polydimethylsiloxane and water-based resin.

6. The cored algae-proof rope of claim 5, wherein: the water-based resin is a water-based polyurethane coating agent, a water-based polyacrylate coating agent, a water-based polyvinyl chloride coating agent or a water-based rubber coating agent, and the solid content is 40-60%.

7. The cored algae-proof rope of claim 1, wherein: the synthesis process of the algae-proof coating agent comprises the following steps: in a reaction container, mixing cetylpyridinium chloride and chitosan according to a weight ratio of 2: 1, reacting at the temperature of 70-90 ℃ for 7-9 h to obtain cetylpyridinium chloride modified chitosan; adding 5-10 parts of cetylpyridinium chloride modified chitosan, 5-10 parts of carbon hydroxyl polydimethylsiloxane, 30-40 parts of water-based resin, 3-5 parts of catalyst and 30-55 parts of deionized water under the protection of nitrogen, reacting for 2-4 h at 60-90 ℃, and then adding 2-5 parts of chain extender to obtain the anti-algae coating agent.

8. A method for manufacturing a core-spun algae-proof rope is characterized in that: the method comprises the following steps:

step A, preparing a rope by an inner core layer:

twisting and twisting synthetic fibers with a preset number of composition to obtain a strand, and weaving or twisting the strand to obtain an inner core layer rope;

step B, coating an outer skin layer:

1) and (3) weaving structure: carrying out primary twisting on the synthetic fibers with preset number of twists according to half S twisting direction and half Z twisting direction to obtain S-twisted sheath folded yarns and Z-twisted sheath folded yarns; the S-twisted sheath compound yarns and the Z-twisted sheath compound yarns are woven in a staggered mode to form outer sheath layers, and the outer sheath layers are tightly wrapped outside the inner core layer rope to obtain the core-spun rope; soaking the obtained core-spun rope in an algae-proof coating agent, taking out, draining off excessive glue solution, and drying to obtain the core-spun algae-proof rope with a braided outer skin layer;

2) the plastic coating structure: and feeding the rope of the inner core layer into a plastic coating machine, and performing plastic coating, pultrusion, curing and molding through a circular die orifice to obtain the core-spun algae-proof rope with the outer skin layer of a plastic coating structure.

9. The method for manufacturing the cored algae-proof rope according to claim 8, wherein the method comprises the following steps: the drying conditions in the step of finishing the algae-proof coating in the step B are as follows: the drying temperature is 80-120 ℃, and the drying time is 5-10 min.

Technical Field

The invention relates to a core-spun algae-prevention rope and a manufacturing method thereof, and belongs to the technical field of ropes and manufacturing thereof.

Background

In the field of marine culture, the service life of a rope made of synthetic fiber spinning is greatly shortened due to the attachment of seaweed. The rope is wrapped by seaweed and adsorbed to inhibit the growth of seafood such as thallus Porphyrae. Traditionally, the method for preventing seaweed in the rope for laver cultivation is to treat the surface of rope fibers by using a heavy metal ion salt solution containing copper, tin, mercury, lead and the like, and prevent the adsorption and growth of the seaweed by releasing toxic metal ions, but the method is easy to cause pollution to marine environment and cultivated organisms.

Disclosure of Invention

In order to solve the problems, the invention provides a core-spun algae-proof rope and a manufacturing method thereof, and the specific technical scheme is as follows,

the utility model provides a algae rope is prevented to covering core, includes ectotheca and inner core layer, the ectotheca closely cladding is outside at the inner core layer, the structure is moulded for weaving structure or package to the ectotheca, for the exotheca overcoat algae-proof coating of weaving structure, the inner core layer is the structure of weaving or the system of twisting of synthetic fiber rope strand.

Preferably, the braided structure of the outer skin layer is braided by half of S twist direction and half of Z twist direction synthetic fiber strands.

Preferably, the plastic-coated structure of the outer skin layer is formed by melting, extruding and coating plastic of plastic particles, and the thickness of the plastic-coated structure is 0.5-3 mm.

Furthermore, the plastic particles are one of PVC particles, TPE particles, ABS environment-friendly particles, TPU particles and TPR particles.

Preferably, the algae-prevention coating is a toughness protective body formed by copolymerizing cetylpyridinium chloride modified chitosan, carbon hydroxyl polydimethylsiloxane and water-based resin.

Preferably, the aqueous resin is an aqueous polyurethane coating agent, an aqueous polyacrylate coating agent, an aqueous polyvinyl chloride coating agent or an aqueous rubber coating agent, and the solid content is 40-60%.

Preferably, the synthesis process of the algae-proof coating agent comprises the following steps: in a reaction container, mixing cetylpyridinium chloride and chitosan according to a weight ratio of 2: 1, reacting at the temperature of 70-90 ℃ for 7-9 h to obtain cetylpyridinium chloride modified chitosan; adding 5-10 parts of cetylpyridinium chloride modified chitosan, 5-10 parts of carbon hydroxyl polydimethylsiloxane, 30-40 parts of water-based resin, 3-5 parts of catalyst and 30-55 parts of deionized water under the protection of nitrogen, reacting for 2-4 h at 60-90 ℃, and then adding 2-5 parts of chain extender to obtain the anti-algae coating agent.

A method for manufacturing a core-spun algae-proof rope comprises the following steps:

step A, preparing a rope by an inner core layer:

twisting and twisting synthetic fibers with a preset number of composition to obtain a strand, and weaving or twisting the strand to obtain an inner core layer rope;

step B, coating an outer skin layer:

1) and (3) weaving structure: carrying out primary twisting on the synthetic fibers with preset number of twists according to half S twisting direction and half Z twisting direction to obtain S-twisted sheath folded yarns and Z-twisted sheath folded yarns; the S-twisted sheath compound yarns and the Z-twisted sheath compound yarns are woven in a staggered mode to form outer sheath layers, and the outer sheath layers are tightly wrapped outside the inner core layer rope to obtain the core-spun rope; soaking the obtained core-spun rope in an algae-proof coating agent, taking out, draining off excessive glue solution, and drying to obtain the core-spun algae-proof rope with a braided outer skin layer;

2) the plastic coating structure: and feeding the rope of the inner core layer into a plastic coating machine, and performing plastic coating, pultrusion, curing and molding through a circular die orifice to obtain the core-spun algae-proof rope with the outer skin layer of a plastic coating structure.

Further, the drying conditions in the step of finishing the algae-proof coating in the step B are as follows: the drying temperature is 80-120 ℃, and the drying time is 5-10 min.

The invention has simple and convenient manufacture and excellent performance, can not only improve the performances of breaking strength, wear resistance and the like of the rope, but also obviously reduce the initial biological attachment amount generated in the early stage of green tide, thereby achieving the aim of preventing algae.

Drawings

Fig. 1 is a schematic structural view of the core-spun algae-proof rope with the outer skin layer of the invention being a woven structure.

Fig. 2 is a schematic structural view of the core-spun algae-proof rope with the outer skin layer of the plastic-coated structure.

In the figure: 1. an inner core layer; 2. an outer skin layer; 3. an anti-algae coating.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1 and 2, the core-spun algae-proof rope comprises an outer skin layer 2 and an inner core layer 1, wherein the outer skin layer 2 is tightly wrapped outside the inner core layer 1, the outer skin layer 2 is of a woven structure or a plastic-wrapped structure, an algae-proof coating 3 is coated outside the outer skin layer 2 of the woven structure, and the inner core layer 1 is of a woven structure or a twisted structure of a synthetic fiber rope strand.

The braided structure of the outer skin layer 2 is braided by half of S-twist direction and half of Z-twist direction synthetic fiber strands. The plastic-coated structure of the outer skin layer 2 is formed by melting, extruding and coating plastic of plastic particles, and the thickness of the plastic-coated structure is 0.5-3 mm. The plastic particles are one of PVC particles, TPE particles, ABS environment-friendly particles, TPU particles and TPR particles.

The algae-proof coating 3 is a toughness protective body formed by copolymerizing cetylpyridinium chloride amine modified chitosan, carbon hydroxyl polydimethylsiloxane and water-based resin. The water-based resin is a water-based polyurethane coating agent, a water-based polyacrylate coating agent, a water-based polyvinyl chloride coating agent or a water-based rubber coating agent, and the solid content is 40-60%.

The synthesis process of the algae-proof coating agent comprises the following steps: in a reaction container, mixing cetylpyridinium chloride and chitosan according to a weight ratio of 2: 1, reacting at the temperature of 70-90 ℃ for 7-9 h to obtain cetylpyridinium chloride modified chitosan; adding 5-10 parts of cetylpyridinium chloride modified chitosan, 5-10 parts of carbon hydroxyl polydimethylsiloxane, 30-40 parts of water-based resin, 3-5 parts of catalyst and 30-55 parts of deionized water under the protection of nitrogen, reacting for 2-4 h at 60-90 ℃, and then adding 2-5 parts of chain extender to obtain the anti-algae coating agent.

A method for manufacturing a core-spun algae-proof rope comprises the following steps:

step A, preparing a rope by using an inner core layer 1:

twisting and twisting synthetic fibers with a preset number of composition to obtain a strand, and weaving or twisting the strand to obtain an inner core layer rope;

step B, coating an outer skin layer 2:

1) and (3) weaving structure: carrying out primary twisting on the synthetic fibers with preset number of twists according to half S twisting direction and half Z twisting direction to obtain S-twisted sheath folded yarns and Z-twisted sheath folded yarns; the S twisted sheath compound yarns and the Z twisted sheath compound yarns are woven in a staggered mode to form outer sheath layers, and the outer sheath layers 2 are tightly wrapped outside the rope of the inner core layer 1 to obtain a core-spun rope; and soaking the obtained core-spun rope in the anti-algae coating agent, taking out, draining off redundant glue solution, and drying to obtain the core-spun anti-algae rope with the outer skin layer 2 of a woven structure. The drying temperature is 80-120 ℃, and the drying time is 5-10 min.

2) The plastic coating structure: and feeding the rope of the inner core layer 1 into a plastic coating machine, and performing plastic coating, pultrusion, curing and molding through a circular die orifice to obtain the core-spun algae-proof rope with the outer skin layer 2 in a plastic coating structure.

The rope is woven and coated, and the anti-algae coating is finished, so that the coated rope is smooth, mellow and full in surface and is easy to finish by the anti-algae coating 3. The anti-algae coating is prepared by copolymerizing cetylpyridinium chloride modified chitosan, carbon hydroxyl polydimethylsiloxane and water-based resin, and the cetylpyridinium chloride belongs to a nitrogen-containing cationic surfactant and is mainly used for sterilization and disinfection. Under the same use condition, the product has better killing rate on microscopic propagules such as bacteria and the like than dodecyl dimethyl benzyl ammonium chloride, dodecyl dimethyl benzyl ammonium bromide and other commonly used quaternary ammonium salt bactericides, and the cetylpyridinium chloride and the marine organism chitosan are modified by chemical modification to further improve the bactericidal effect, thereby effectively preventing the germination and growth of seaweed.

The rope is coated with plastic, so that the attachment and germination of the seaweed can be inhibited, the biomass of the seaweed is reduced, and the large-scale outbreak of the seaweed is avoided. The plastic particle coating layer has the obvious characteristics of low manufacturing cost, smooth product surface, excellent mechanical property and the like, and can be used for preventing marine organisms from attaching.

Example 1:

a core-spun algae-proof rope comprises an outer skin layer 2 and an inner core layer 1, wherein the outer skin layer 2 is tightly wrapped outside the inner core layer 1, the outer skin layer 2 is of a woven structure, an algae-proof coating is coated outside the outer skin layer 2, and the outer skin layer 2 is an outer sleeve body formed by weaving ultrahigh molecular weight polyethylene fiber strands in 16S twisting directions and 16Z twisting directions; the inner core layer 1 is an inner core body formed by twisting 3 synthetic PP flat filament fiber rope strands; the algae-proof coating 3 is a toughness protective body formed by copolymerizing cetylpyridinium chloride amine modified chitosan, carbon hydroxyl polydimethylsiloxane and water-based resin.

A method for manufacturing a core-spun algae-proof rope comprises the following steps:

step A, preparing a rope by using an inner core layer 1: carrying out primary twisting on 4-ply PP fibers, wherein the twist number is 60 twists/m, and the twisting direction is Z direction, so as to obtain rope yarns for strand making; and (3) carrying out compound twisting on 22 rope yarns for strand making, wherein the twist number is 40 twists/m, and the twisting direction is S direction, so as to obtain rope strands for rope twisting, and carrying out rope twisting on 3 rope strands for rope twisting according to the twist number of 15 twists/m and the twisting direction S direction, so as to obtain the PP three-strand rope twisting.

Step B, coating an outer skin layer 2: carrying out primary twisting on the 3-ply ultrahigh molecular weight polyethylene fibers according to 16S twisting directions and 16Z twisting directions to obtain S-twisted sheath folded yarns and Z-twisted sheath folded yarns; the S-twisted sheath compound yarns and the Z-twisted sheath compound yarns are woven in a staggered mode to form outer sheath layers 2, and the outer sheath layers 2 are tightly wrapped outside the inner core layer 1 to obtain the core-spun rope; and soaking the obtained core-spun rope in the algae-proof coating agent, taking out, draining off excessive glue solution, and drying at 80 ℃ for 5min to obtain the core-spun algae-proof rope.

In this embodiment, the synthesis process of the algae-preventing coating agent is as follows: mixing cetylpyridinium chloride and chitosan according to a weight ratio of 2: 1, reacting at the temperature of 70 ℃ for 7 hours to obtain cetylpyridinium chloride modified chitosan; adding 5 parts of cetylpyridinium chloride modified chitosan, 5 parts of carbon hydroxyl polydimethylsiloxane, 30 parts of water-based resin and 3 parts of catalyst under the protection of nitrogen, 55 parts of deionized water, reacting for 2 hours at 60 ℃, and then adding 2 parts of chain extender to obtain the product.

Example 2:

a core-spun anti-algae rope comprises an outer skin layer 2 and an inner core layer 1, wherein the outer skin layer 2 is tightly wrapped outside the inner core layer, the outer skin layer 2 is of a woven structure, an anti-algae coating is coated outside the outer skin layer 2, and the outer skin layer 2 is an outer sleeve body formed by weaving 24S-twisted aramid fiber/nylon composite fiber strands and 24Z-twisted aramid fiber/nylon composite fiber strands; the inner core layer 1 is an inner core body woven by 12S-twist-direction polyester fiber strands and 12Z-twist-direction polyester fiber strands; the algae-proof coating 3 is a toughness protective body formed by copolymerizing cetylpyridinium chloride amine modified chitosan, carbon hydroxyl polydimethylsiloxane and water-based resin.

A method for manufacturing a core-spun algae-proof rope comprises the following steps:

step A, preparing a rope by using an inner core layer 1: taking 6-ply polyester fiber, and carrying out primary twisting in the S twisting direction and the Z twisting direction with the twist number of 40 twists/m to obtain an S-twist inner core folded yarn and a Z-twist inner core folded yarn; and (3) interweaving the 12S-direction inner core strands and the 12Z-direction inner core strands to obtain the 24-strand terylene circular knitting rope.

Step B, coating an outer skin layer 2: carrying out primary twisting on 3-ply aramid/chinlon composite fibers according to 24S twisting directions and 24Z twisting directions to obtain S-twisted sheath compound yarns and Z-twisted sheath compound yarns; the S-twisted sheath compound yarns and the Z-twisted sheath compound yarns are woven in a staggered mode to form outer sheath layers 2, and the outer sheath layers 2 are tightly wrapped outside the inner core layer 1 to obtain the core-spun rope; and soaking the obtained core-spun rope in the algae-proof coating agent, taking out, draining off redundant glue solution, and drying at 120 ℃ for 10min to obtain the core-spun algae-proof rope.

In this embodiment, the synthesis process of the algae-preventing coating agent is as follows: mixing cetylpyridinium chloride and chitosan according to a weight ratio of 2: 1, reacting at 90 ℃ for 9h to obtain cetylpyridinium chloride modified chitosan; adding 10 parts of cetylpyridinium chloride modified chitosan, 10 parts of carbon hydroxyl polydimethylsiloxane, 40 parts of water-based resin and 5 parts of catalyst under the protection of nitrogen, reacting for 4 hours at 90 ℃, and then adding 5 parts of chain extender to obtain the product.

Example 3:

a core-spun anti-algae rope comprises an outer skin layer 2 and an inner core layer 1, wherein the outer skin layer 2 is tightly wrapped outside the inner core layer 1, the outer skin layer 2 is of a woven structure, an anti-algae coating is coated outside the outer skin layer 2, and the outer skin layer 2 is an outer sleeve body formed by weaving 24S-twisted aramid/polyamide composite fiber strands and 24Z-twisted aramid/polyamide composite fiber strands; the inner core layer 1 is an inner core body woven by 12S-twist-direction polyester fiber strands and 12Z-twist-direction polyester fiber strands; the algae-proof coating 3 is a toughness protective body formed by copolymerizing cetylpyridinium chloride amine modified chitosan, carbon hydroxyl polydimethylsiloxane and water-based resin.

A method for manufacturing a core-spun algae-proof rope comprises the following steps:

step A, preparing a rope by using an inner core layer 1: taking 6-ply polyester fiber, and carrying out primary twisting in the S twisting direction and the Z twisting direction with the twist number of 40 twists/m to obtain an S-twist inner core folded yarn and a Z-twist inner core folded yarn; and (3) interweaving the 12S-direction inner core strands and the 12Z-direction inner core strands to obtain the 24-strand terylene circular knitting rope.

Step B, coating an outer skin layer 2: carrying out primary twisting on 3-ply aramid/chinlon composite fibers according to 24S twisting directions and 24Z twisting directions to obtain S-twisted sheath compound yarns and Z-twisted sheath compound yarns; the S-twisted sheath compound yarns and the Z-twisted sheath compound yarns are woven in a staggered mode to form outer sheath layers 2, and the outer sheath layers 2 are tightly wrapped outside the inner core layer 1 to obtain the core-spun rope; and soaking the obtained core-spun rope in the algae-proof coating agent, taking out, draining off redundant glue solution, and drying at 100 ℃ for 8min to obtain the core-spun algae-proof rope.

In this embodiment, the synthesis process of the algae-preventing coating agent is as follows: mixing cetylpyridinium chloride and chitosan according to a weight ratio of 2: 1, reacting at the temperature of 80 ℃ for 8 hours to obtain cetylpyridinium chloride modified chitosan; adding 8 parts of cetylpyridinium chloride modified chitosan, 8 parts of carbon hydroxyl polydimethylsiloxane, 35 parts of water-based resin and 4 parts of catalyst under the protection of nitrogen, reacting for 3 hours at 75 ℃, and then adding 4 parts of chain extender to obtain the product.

Example 4:

a core-spun anti-algae rope comprises an outer skin layer 2 and an inner core layer 1, wherein the outer skin layer 2 is tightly coated outside the inner core layer 1, the outer skin layer 2 is a plastic-coated structure, and the outer skin layer 2 is an outer sleeve body formed by melting, extruding and coating PVC particles; the inner core layer 1 is an inner core body formed by twisting 3 synthetic PP flat filament fiber strands.

A method for manufacturing a core-spun algae-proof rope comprises the following steps:

step A, preparing a rope by using an inner core layer 1: carrying out primary twisting on 4-ply PP fibers, wherein the twist number is 60 twists/m, and the twisting direction is Z direction, so as to obtain rope yarns for strand making; and (3) carrying out compound twisting on 22 rope yarns for strand making, wherein the twist number is 40 twists/m, and the twisting direction is S direction, so as to obtain rope strands for rope twisting, and carrying out rope twisting on 3 rope strands for rope twisting according to the twist number of 15 twists/m and the twisting direction S direction, so as to obtain the PP three-strand rope twisting.

Step B, coating an outer skin layer 2: and feeding the rope of the inner core layer 1 into a plastic coating machine, and performing PVC plastic coating, pultrusion, curing and molding through a circular die to obtain the plastic coating structure algae-proof rope with the PVC film thickness of 3 mm.

Example 5:

a core-spun algae-proof rope comprises an outer skin layer 2 and an inner core layer 1, wherein the outer skin layer 2 is tightly coated outside the inner core layer 1, the outer skin layer 2 is of a plastic-coated structure, and the outer skin layer 2 is an outer sleeve body formed by melting, extruding and coating TPE (thermoplastic elastomer) particles; the inner core layer 1 is an inner core body formed by twisting 6S-twist-direction and 6Z-twist-direction ultrahigh molecular weight polyethylene fiber strands.

Step A, preparing a rope by using an inner core layer 1: and (3) primarily twisting 36-ply ultrahigh molecular weight polyethylene fibers in an S twisting direction and a Z twisting direction, wherein the twisting degree is 40 twists per meter, so that an S-twisted inner core strand and a Z-twisted inner core strand are obtained, and 6S-twisted strand strands and 6Z-twisted strand strands are adopted to be woven in a staggered manner, so that the ultrahigh molecular weight polyethylene 12-woven round rope is obtained.

Step B, coating an outer skin layer 2: and feeding the rope of the inner core layer 1 into a plastic coating machine, and performing TPE plastic coating, pultrusion, curing and molding through a circular die to obtain the plastic-coated structure algae-proof rope with the TPE film thickness of 1.5 mm.

And (3) strength test: the strength test results of the rope before coating and the core-spun anti-algae rope in comparative examples 1 to 5 are shown in table 1.

Table 1:

chlorella attachment test: chlorella is selected as an experimental object, the rope before coating and the core-spun algae-proof rope in the examples 1-5 are subjected to an algae static attaching experiment and a simulated static attaching algae scouring experiment to research the algae-proof performance of the rope, and the test results are shown in Table 2.

Table 2:

from the test results, the core-spun algae-proof rope obtained by the manufacturing method has very obvious advantages compared with a synthetic fiber rope, not only has higher breaking strength, but also can obviously reduce the static attachment amount of algae, is easy to wash and prolongs the service life of the rope.

Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes in the embodiments and/or modifications of the invention can be made, and equivalents and modifications of some features of the invention can be made without departing from the spirit and scope of the invention.