阅读说明：本技术 一种医用水凝胶卷材及其制备方法 (Medical hydrogel coiled material and preparation method thereof ) 是由 钱峙涛 侯巍 李宁 于 2021-06-24 设计创作，主要内容包括：一种医用水凝胶卷材及其制备方法,包括背衬层、水凝胶层及防粘层,所述水凝胶层涂覆于背衬层上,所述水凝胶层上还附着黏贴有防粘层；医用水凝胶卷材的制备方法,第一步：油相配置；第二步：水相配置；第三步：真空搅拌；第四步：涂布收卷；本发明提供了一种快速固化的水凝胶卷材及其制备方法,本产品的组分真空下搅拌能够快速充分的吸水锁水；双烘道、双风道、的生产工艺,可以迅速升温、固化又不破坏产品的理化性质；第一烘道迅速对产品表面及心部迅速升温,第一风道将产品降温至表面、心部同温,消除温度差,保证在经过第二烘道时,内外均匀固化,第二风道快速降温保证水分不流失。(A medical hydrogel coiled material and a preparation method thereof comprise a back lining layer, a hydrogel layer and an anti-sticking layer, wherein the hydrogel layer is coated on the back lining layer, and the anti-sticking layer is adhered to the hydrogel layer; the preparation method of the medical hydrogel coiled material comprises the following steps: preparing an oil phase; the second step is that: preparing a water phase; the third step: stirring in vacuum; the fourth step: coating and rolling; the invention provides a fast-curing hydrogel coiled material and a preparation method thereof, and the components of the product can be stirred under vacuum to quickly and fully absorb and lock water; the production process of double drying tunnels and double air ducts can quickly raise the temperature and solidify without damaging the physical and chemical properties of the product; the first drying tunnel rapidly heats the surface and the core of the product, the first air duct cools the product to the same temperature of the surface and the core, the temperature difference is eliminated, the uniform solidification inside and outside is ensured when the product passes through the second drying tunnel, and the rapid cooling of the second air duct ensures that the water is not lost.)

1. A medical hydrogel coiled material comprises a back lining layer, a hydrogel layer and an anti-sticking layer, wherein the hydrogel layer is coated on the back lining layer, and the anti-sticking layer is adhered to the hydrogel layer; the hydrogel layer composition comprises: 15-30 parts of glycerol, 4-8 parts of sodium polyacrylate, 0.02-0.2 part of ethylene diamine tetraacetic acid disodium, 0.1-0.25 part of dihydroxyaluminum glycinate, 0.01-0.1 part of crystalline aluminum chloride, 60-80 parts of deionized water, 0.08-0.30 part of tartaric acid and 0.5-2 parts of polyacrylic acid.

2. A roll of medical hydrogel according to claim 1 wherein the hydrogel layer composition further comprises 0.3 parts of a preservative.

3. The medical hydrogel roll as claimed in claim 1, wherein the backing layer is made of spunlace nonwoven fabric, conductive carbon film, PET or PE.

4. The medical hydrogel roll as claimed in claim 1, wherein the anti-sticking layer is made of CPP embossed film or PP-conductive isolating film or PET or PE or silicone-coated glassine paper.

5. A method for producing a roll of medical hydrogel according to any of claims 1 to 4, characterized by comprising the steps of:

the first step is as follows: preparing an oil phase; weighing glycerol according to a ratio, adding powdery sodium polyacrylate, disodium ethylene diamine tetraacetate, dihydroxyaluminum glycinate and crystalline aluminum chloride into a pot, pressing the powdery material by using a stirrer, and after the glycerol is soaked in the powdery material, stirring at a medium speed until the glycerol and the powdery material are uniformly mixed, wherein the stirring speed is 50-60 rpm;

the second step is that: preparing a water phase; adding deionized water into a barrel according to a ratio, adding polyacrylic acid according to a ratio, stirring uniformly until no obvious particles are visible, pouring tartaric acid and a preservative which are weighed according to a ratio into water, and stirring uniformly;

the third step: stirring in vacuum; pouring the oil phase and the water phase into a vacuum stirring tank in sequence, then vacuumizing to-80 mpa, quickly stirring for 2-3 minutes at the stirring speed of 90-100 rpm, and slowly stirring for 5-6 minutes at the stirring speed of 30-50 rpm; then, putting the hydrogel uniformly mixed and stirred by the vacuum stirrer into a coating machine;

the fourth step: coating and rolling; coating the hydrogel prepared in the third step on a back lining layer, and then coating an anti-sticking layer on the upper surface of the hydrogel; then sequentially passing through a first drying tunnel, a first air duct, a second drying tunnel and a second air duct, and then rolling the product; the diameter of the roll is 3-6 cun.

6. The method for preparing a medical hydrogel roll according to claim 5, wherein the first drying tunnel has a temperature of 80 ℃ to 120 ℃ and a length of 0.3m to 0.6 m; the temperature of air blown by the first air duct fan is 40-60 ℃, and the length of the air blown by the first air duct fan is 0.3-0.5 m; the temperature of the second drying channel is 60-80 ℃, and the length is 1.5-2.5 m; the temperature of the second air duct is 10-15 ℃, and the length of the second air duct is 0.5-1 m; the speed of the coiled material passing through the first drying tunnel, the first air duct, the second drying tunnel and the second air duct is 1.5m/min-2 m/min.

The technical field is as follows:

the invention relates to the technical field of hydrogel coiled materials, in particular to a medical hydrogel coiled material and a preparation method thereof.

Background art:

hydrogels (hydrogels) are gels that use water as the dispersion medium. The water-soluble polymer with a reticular cross-linked structure is a cross-linked polymer which is formed by introducing a part of hydrophobic groups and hydrophilic residues into the water-soluble polymer, wherein the hydrophilic residues are combined with water molecules to connect the water molecules in the reticular structure, and the hydrophobic residues swell when meeting water. Is a polymer network system, has soft property, can keep a certain shape, and can absorb a large amount of water.

The production process of medical hydrogel products in the market at present mainly comprises product coating, sheet slitting and cutting after curing, wherein the general products can be cured after being slit for more than 12 hours, and a large number of drying racks are needed for placing the products during batch production, so that the production efficiency of the products is influenced, and a large amount of space is occupied.

The invention content is as follows:

in order to solve the problems and overcome the defects of the prior art, the invention aims to provide a medical hydrogel coiled material and a preparation method thereof; solves the problems of long curing time and large space occupation of the existing hydrogel product.

In order to achieve the purpose, the technical scheme of the invention is that the medical hydrogel coiled material comprises a back lining layer, a hydrogel layer and an anti-sticking layer, wherein the hydrogel layer is coated on the back lining layer, and the anti-sticking layer is adhered to the hydrogel layer; the hydrogel layer composition comprises: 15-30 parts of glycerol, 4-8 parts of sodium polyacrylate, 0.02-0.2 part of ethylene diamine tetraacetic acid disodium, 0.1-0.25 part of dihydroxyaluminum glycinate, 0.01-0.1 part of crystalline aluminum chloride, 60-80 parts of deionized water, 0.08-0.30 part of tartaric acid and 0.5-2 parts of polyacrylic acid.

Further, the hydrogel layer composition also included 0.3 parts of a preservative.

Furthermore, the backing layer is made of spunlace nonwoven fabric, conductive carbon film, PET or PE.

Furthermore, the anti-sticking layer is made of a CPP embossed film, a PP guide isolation film, PET or PE or silicon-coated glassine paper.

The preparation method of the medical hydrogel coiled material comprises the following steps:

the first step is as follows: preparing an oil phase; weighing glycerol according to a ratio, adding powdery sodium polyacrylate, disodium ethylene diamine tetraacetate, dihydroxyaluminum glycinate and crystalline aluminum chloride into a pot, pressing the powdery material by using a stirrer, and after the glycerol is soaked in the powdery material, stirring at a medium speed until the glycerol and the powdery material are uniformly mixed, wherein the stirring speed is 50-60 rpm;

the second step is that: preparing a water phase; adding deionized water into a barrel according to a ratio, adding polyacrylic acid according to a ratio, stirring uniformly until no obvious particles are visible, pouring tartaric acid and a preservative which are weighed according to a ratio into water, and stirring uniformly;

the third step: stirring in vacuum; pouring the oil phase and the water phase into a vacuum stirring tank in sequence, then vacuumizing to-80 mpa, quickly stirring for 2-3 minutes at the stirring speed of 90-100 rpm, and slowly stirring for 5-6 minutes at the stirring speed of 30-50 rpm; then, putting the hydrogel uniformly mixed and stirred by the vacuum stirrer into a coating machine;

the fourth step: coating and rolling; coating the hydrogel prepared in the third step on a back lining layer, and then coating an anti-sticking layer on the upper surface of the hydrogel; then sequentially passing through a first drying tunnel, a first air duct, a second drying tunnel and a second air duct, and then rolling the product; the diameter of the roll is 3-6 cun.

Furthermore, the temperature of the first drying channel is 80-120 ℃, and the length of the first drying channel is 0.3-0.6 m; the temperature of air blown by the first air duct fan is 40-60 ℃, and the length of the air blown by the first air duct fan is 0.3-0.5 m; the temperature of the second drying channel is 60-80 ℃, and the length is 1.5-2.5 m; the temperature of the second air duct is 10-15 ℃, and the length of the second air duct is 0.5-1 m; the speed of the coiled material passing through the first drying tunnel, the first air duct, the second drying tunnel and the second air duct is 1.5m/min-2 m/min.

The invention has the beneficial effects that: the invention provides a fast-curing hydrogel coiled material and a preparation method thereof, and the components of the product can be stirred under vacuum to quickly and fully absorb and lock water; the production process of double drying tunnels and double air ducts can quickly raise the temperature and solidify without damaging the physical and chemical properties of the product; the first drying tunnel rapidly heats the surface and the core of the product, the first air duct cools the product to the same temperature of the surface and the core, the temperature difference is eliminated, the uniform solidification inside and outside is ensured when the product passes through the second drying tunnel, and the rapid cooling of the second air duct ensures that the water is not lost.

The specific implementation mode is as follows:

in order to make the implementation objects, technical solutions and advantages of the present invention clearer, the present invention will be described in more detail below with reference to embodiments of the present invention.

A medical hydrogel coiled material comprises a back lining layer, a hydrogel layer and an anti-sticking layer, wherein the hydrogel layer is coated on the back lining layer, and the anti-sticking layer is adhered to the hydrogel layer; the hydrogel layer composition comprises: 15-30 parts of glycerol, 4-8 parts of sodium polyacrylate, 0.02-0.2 part of ethylene diamine tetraacetic acid disodium, 0.1-0.25 part of dihydroxyaluminum glycinate, 0.01-0.1 part of crystalline aluminum chloride, 60-80 parts of deionized water, 0.08-0.30 part of tartaric acid and 0.5-2 parts of polyacrylic acid.

The hydrogel layer component also includes 0.3 parts of preservative.

The backing layer is made of spunlace nonwoven fabric, conductive carbon film, PET or PE.

The anti-sticking layer is made of a CPP embossed film, a PP isolation film, PET, PE or silicon-coated glassine paper.

The preparation method of the medical hydrogel coiled material comprises the following steps:

the first step is as follows: preparing an oil phase; weighing glycerol according to a ratio, adding powdery sodium polyacrylate, disodium ethylene diamine tetraacetate, dihydroxyaluminum glycinate and crystalline aluminum chloride into a pot, pressing the powdery material by using a stirrer, and after the glycerol is soaked in the powdery material, stirring at a medium speed until the glycerol and the powdery material are uniformly mixed, wherein the stirring speed is 50-60 rpm;

the second step is that: preparing a water phase; adding deionized water into a barrel according to a ratio, adding polyacrylic acid according to a ratio, stirring uniformly until no obvious particles are visible, pouring tartaric acid and a preservative which are weighed according to a ratio into water, and stirring uniformly;

the third step: stirring in vacuum; pouring the oil phase and the water phase into a vacuum stirring tank in sequence, then vacuumizing to-80 mpa, quickly stirring for 2-3 minutes at the stirring speed of 90-100 rpm, and slowly stirring for 5-6 minutes at the stirring speed of 30-50 rpm; then, putting the hydrogel uniformly mixed and stirred by the vacuum stirrer into a coating machine;

the fourth step: coating and rolling; coating the hydrogel prepared in the third step on a back lining layer, and then coating an anti-sticking layer on the upper surface of the hydrogel; then sequentially passing through a first drying tunnel, a first air duct, a second drying tunnel and a second air duct, and then rolling the product; the diameter of the roll is 3-6 cun.

Furthermore, the temperature of the first drying channel is 80-120 ℃, and the length of the first drying channel is 0.3-0.6 m; the temperature of air blown by the first air duct fan is 40-60 ℃, and the length of the air blown by the first air duct fan is 0.3-0.5 m; the temperature of the second drying channel is 60-80 ℃, and the length is 1.5-2.5 m; the temperature of the second air duct is 10-15 ℃, and the length of the second air duct is 0.5-1 m; the speed of the coiled material passing through the first drying tunnel, the first air duct, the second drying tunnel and the second air duct is 1.5m/min-2 m/min.

Example 1

A medical hydrogel coiled material and a preparation method thereof are as follows:

oil phase preparation: weighing 25 parts of glycerol according to a ratio, adding 5 parts of sodium polyacrylate, 0.1 part of disodium ethylene diamine tetraacetate, 0.15 part of dihydroxyaluminum glycerate and 0.05 part of crystalline aluminum chloride into a pot, pressing powder by using a stirrer to soak the glycerol into the powder, stirring at a medium speed for 5 minutes to fully and uniformly stir the glycerol and the powder; preparing a water phase: 68.15 parts of deionized water is added into a barrel according to the formula, 1 part of polyacrylic acid is added according to the formula, the mixture is stirred uniformly until no obvious particles are visible in water, and then 0.25 part of tartaric acid and 0.3 part of preservative are weighed and poured into water to be stirred uniformly; and (3) stirring in vacuum: pouring the oil phase and the water phase into a vacuum stirring tank in sequence, then vacuumizing to-80 mpa, quickly stirring for 2 minutes at the stirring speed of 90rpm, and slowly stirring for 5 minutes at the stirring speed of 30 rpm; the hydrogel mixed and stirred by the vacuum stirrer can be put into a coating machine for coating; coating the prepared hydrogel on a back lining layer, then coating an anti-sticking layer, then sequentially passing through a first drying channel, a first air channel, a second drying channel and a second air channel, and then rolling the product. And simultaneously recording the curing time of the product and the edge flow-extending condition of the colloid after the product is rolled.

The temperature of the first drying channel is 80 ℃, and the length of the first drying channel is 0.3 m; the temperature of air blown by the first air duct fan is 40 ℃, and the length of the air blown by the first air duct fan is 0.3 m; the temperature of the second drying channel is 60 ℃, and the length of the second drying channel is 1.5 m; the temperature of the second air duct is 10 ℃, and the length of the second air duct is 0.5 m; the speed of the coiled material passing through the first drying tunnel, the first air duct, the second drying tunnel and the second air duct is 1.5 m/min.

Example 2

A medical hydrogel coiled material and a preparation method thereof are as follows:

oil phase preparation: weighing 25 parts of glycerol according to a ratio, adding 5 parts of sodium polyacrylate, 0.1 part of disodium ethylene diamine tetraacetate, 0.2 part of dihydroxyaluminum glycinate and 0.05 part of crystalline aluminum chloride into a pot, pressing powder by using a stirrer to soak the glycerol into the powder, stirring at a medium speed for 5 minutes to fully and uniformly stir the glycerol and the powder; preparing a water phase: adding 68.1 parts of deionized water into a barrel according to a formula, adding 1 part of polyacrylic acid according to the formula, uniformly stirring until no obvious particles are visible in water, and pouring 0.25 part of tartaric acid and 0.3 part of preservative into water and uniformly stirring; and (3) stirring in vacuum: pouring the oil phase and the water phase into a vacuum stirring tank in sequence, then vacuumizing to-80 mpa, quickly stirring for 3 minutes at the stirring speed of 100rpm, and slowly stirring for 6 minutes at the stirring speed of 50 rpm; the hydrogel mixed and stirred by the vacuum stirrer can be put into a coating machine for coating. Coating the prepared hydrogel on a back lining layer, coating an anti-sticking layer, sequentially passing through a first drying channel, a first air channel, a second drying channel and a second air channel, and then rolling the product. And simultaneously recording the curing time of the product and the edge flow-extending condition of the colloid after the product is rolled.

The temperature of the first drying channel is 120 ℃, and the length of the first drying channel is 0.6 m; the temperature of air blown by the first air duct fan is 60 ℃, and the length of the air blown by the first air duct fan is 0.5 m; the temperature of the second drying channel is 80 ℃, and the length of the second drying channel is 2.5 m; the temperature of the second air duct is 15 ℃, and the length of the second air duct is 1 m; the speed of the coiled material passing through the first drying tunnel, the first air duct, the second drying tunnel and the second air duct is 2 m/min.

Example 3

A medical hydrogel coiled material and a preparation method thereof are as follows:

oil phase preparation: weighing 30 parts of glycerol according to the proportion, adding 6 parts of sodium polyacrylate, 0.1 part of disodium ethylene diamine tetraacetate, 0.15 part of dihydroxyaluminum glycerate and 0.05 part of crystalline aluminum chloride into a pot, pressing powder by using a stirrer to soak the glycerol into the powder, stirring at a medium speed for 5 minutes to fully and uniformly stir the glycerol and the powder; preparing a water phase: adding 62.15 parts of deionized water into a barrel according to the formula, adding 1 part of polyacrylic acid according to the formula, uniformly stirring until no obvious particles are visible in water, and pouring 0.25 part of tartaric acid and 0.3 part of preservative into water and uniformly stirring;

and (3) stirring in vacuum: pouring the oil phase and the water phase into a vacuum stirring tank in sequence, then vacuumizing to-80 mpa, quickly stirring for 2-3 minutes at the stirring speed of 95rpm, and slowly stirring for 6 minutes at the stirring speed of 40 rpm; the hydrogel mixed and stirred by the vacuum stirrer can be put into a coating machine for coating. Coating the prepared hydrogel on a back lining layer, coating an anti-sticking layer, sequentially passing through a first drying channel, a first air channel, a second drying channel and a second air channel, and then rolling the product. And simultaneously recording the curing time of the product and the edge flow-extending condition of the colloid after the product is rolled.

The temperature of the first drying channel is 100 ℃, and the length of the first drying channel is 0.45 m; the temperature of air blown by the first air duct fan is 50 ℃, and the length of the air blown by the first air duct fan is 0.4 m; the temperature of the second drying channel is 70 ℃, and the length of the second drying channel is 2 m; the temperature of the second air duct is 12 ℃, and the length of the second air duct is 0.8 m; the speed of the coiled material passing through the first drying tunnel, the first air duct, the second drying tunnel and the second air duct is 1.5 m/min.

Example 4

A medical hydrogel coiled material and a preparation method thereof are as follows:

oil phase preparation: weighing 30 parts of glycerol according to the proportion, adding 6 parts of sodium polyacrylate, 0.2 part of disodium ethylene diamine tetraacetate, 0.15 part of dihydroxyaluminum glycerate and 0.05 part of crystalline aluminum chloride into a pot, pressing powder by using a stirrer to soak the glycerol into the powder, stirring at a medium speed for 5 minutes to fully and uniformly stir the glycerol and the powder; preparing a water phase: 62.05 parts of deionized water is added into a barrel according to the formula, 1 part of polyacrylic acid is added according to the formula, the mixture is stirred uniformly until no obvious particles are visible in water, and then 0.25 part of tartaric acid and 0.3 part of preservative are weighed and poured into water to be stirred uniformly; and (3) stirring in vacuum: pouring the oil phase and the water phase into a vacuum stirring tank in sequence, then vacuumizing to-80 mpa, quickly stirring for 2 minutes at the stirring speed of 90rpm, and slowly stirring for 5 minutes at the stirring speed of 30 rpm; the hydrogel mixed and stirred by the vacuum stirrer can be put into a coating machine for coating. Coating the prepared hydrogel on a back lining layer, coating an anti-sticking layer, sequentially passing through a first drying channel, a first air channel, a second drying channel and a second air channel, and then rolling the product. And simultaneously recording the curing time of the product and the edge flow-extending condition of the colloid after the product is rolled.

The temperature of the first drying channel is 80 ℃, and the length of the first drying channel is 0.3 m; the temperature of air blown by the first air duct fan is 40 ℃, and the length of the air blown by the first air duct fan is 0.3 m; the temperature of the second drying channel is 60 ℃, and the length of the second drying channel is 1.5 m; the temperature of the second air duct is 10 ℃, and the length of the second air duct is 0.5 m; the speed of the coiled material passing through the first drying tunnel, the first air duct, the second drying tunnel and the second air duct is 1.5 m/min.

Example 5

A medical hydrogel coiled material and a preparation method thereof are as follows:

oil phase preparation: weighing 30 parts of glycerol according to the proportion, adding 6 parts of sodium polyacrylate, 0.1 part of disodium ethylene diamine tetraacetate, 0.2 part of dihydroxyaluminum glycinate and 0.05 part of crystalline aluminum chloride into a pot, pressing powder by using a stirrer to soak the glycerol into the powder, stirring at medium speed for 5 minutes to fully and uniformly stir the glycerol and the powder; preparing a water phase: adding 62.1 parts of deionized water into a barrel according to the formula, adding 1 part of polyacrylic acid according to the formula, uniformly stirring until no obvious particles are visible in water, and pouring 0.25 part of tartaric acid and 0.3 part of preservative into water and uniformly stirring; and (3) stirring in vacuum: pouring the oil phase and the water phase into a vacuum stirring tank in sequence, then vacuumizing to-80 mpa, quickly stirring for 3 minutes at a stirring speed of 90rpm, and slowly stirring for 5 minutes at a stirring speed of 30-50 rpm; the hydrogel mixed and stirred by the vacuum stirrer can be put into a coating machine for coating. Coating the prepared hydrogel on a back lining layer, coating an anti-sticking layer, sequentially passing through a first drying channel, a first air channel, a second drying channel and a second air channel, and then rolling the product. And simultaneously recording the curing time of the product and the edge flow-extending condition of the colloid after the product is rolled.

The temperature of the first drying channel is 120 ℃, and the length of the first drying channel is 0.6 m; the temperature of air blown by the first air duct fan is 60 ℃, and the length of the air blown by the first air duct fan is 0.3-0.5 m; the temperature of the second drying channel is 80 ℃, and the length of the second drying channel is 2.5 m; the temperature of the second air duct is 15 ℃, and the length of the second air duct is 1 m; the speed of the coiled material passing through the first drying tunnel, the first air duct, the second drying tunnel and the second air duct is 1.5 m/min.

The test method comprises the following steps:

the medical hydrogel coil products prepared in examples 1 to 5 were tested for mechanical properties, coating time, curing time, and edge bleeding after winding. Wherein the mechanical properties include the adhesive force and peel strength of the product.

The adhesive force testing method comprises the following steps: taking 1 piece of a finished product sample, placing the sample in a drying thermostat, drying the sample for 30min at 45 ℃, then recovering to room temperature, placing the sample on a 30cm long inclined plane which forms a 30-degree angle with the horizontal plane, and testing that the sample can stick a No. 32 steel ball with the diameter of 25.4mm, wherein the sample is qualified after the retention time is more than 5S;

the peel strength test method comprises the following steps: taking a finished sample wafer, attaching the hydrogel layer to a plastic plate, fixing the plastic plate, enabling the plastic plate to be vertical to the ground, enabling one end attached above the plastic plate to be downwards reversely folded by 180 degrees and be fixed on a special chuck, vertically hanging a weight with the mass of 150g on the special chuck, and recording the falling time;

recording the coating time to record whether the product can be normally coated in the production process (if the product is cured too fast, the colloid can be coated unevenly or cannot be coated), wherein the curing time of the product is based on the standard that the product cannot deform when being lightly pressed by a 200-gram weight after passing through a drying tunnel, and the time required by the product to pass through the drying tunnel until the product is lightly pressed by the weight and does not deform is recorded;

the edge of the coiled material colloid flows along the condition: recording the coating width of the product during coating, rolling, standing to room temperature, unwinding, and randomly taking 5 sections to record the width of the product.

The data show that the product has excellent adhesive force and peeling strength, meets the production requirement, has short curing time and meets the coating requirement; the edge flow is small, and the batch rapid production in a coiled material form is feasible.

The components of the product can be quickly and fully absorbed and locked by stirring under vacuum; the production process of double drying tunnels and double air ducts can quickly raise the temperature and solidify without damaging the physical and chemical properties of the product; the first drying tunnel rapidly heats the surface and the core of the product, the first air duct cools the product to the same temperature of the surface and the core, the temperature difference is eliminated, the uniform solidification inside and outside is ensured when the product passes through the second drying tunnel, and the rapid cooling of the second air duct ensures that the water is not lost.

Except for the technical features described in the specification, the method is known to the technical personnel in the field.